Using a combination of this old node and The Wayback Machine (entering http://www.perlmonks.org/?node=Best%20Nodes) I've updated my historical list of reputation range (lowest best node-highest best node rep) of best nodes of the month and best nodes of the year as shown below:

• Mar 05 2007 Best nodes month: 83-135 rep, year: 121-194 rep
• Dec 08 2007 Best nodes month: 71-132 rep, year: 115-238 rep

• Apr 24 2008 Best nodes month: 77-111 rep, year: 111-156 rep
• Sep 14 2008 Best nodes month: 59-90 rep, year: 105-180 rep

• Feb 16 2009 Best nodes month: 58-85 rep, year: 91-152 rep
• Apr 28 2009 Best nodes month: 58-134 rep, year: 89-163 rep
• Jun 27 2009 Best nodes month: 63-86 rep, year: 87-141 rep

• Feb 27 2010 Best nodes month: 49-85 rep, year: 86-152 rep
• Apr 29 2010 Best nodes month: 49-105 rep, year: 81-131 rep
• Aug 28 2010 Best nodes month: 46-67 rep, year: 69-135 rep
• Dec 08 2010 Best nodes month: 42-94 rep, year: 72-144 rep

• May 18 2011 Best nodes month: 44-52 rep, year: 68- 99 rep
• Sep 12 2011 Best nodes month: 43-63 rep, year: 64-109 rep
• Nov 12 2011 Best nodes month: 41-62 rep, year: 60-110 rep
• Dec 08 2011 Best nodes month: 46-65 rep, year: 60-98 rep

• Jan 01 2012 Best nodes month: 43-66 rep, year: 62-98 rep
• Feb 01 2012 Best nodes month 37-51 rep, year: 60-79 rep
• Mar 01 2012 Best nodes month 40-62 rep, year: 61-80 rep
• Apr 01 2012 Best nodes month 39-52 rep, year: 59-82 rep
• May 01 2012 Best nodes month 41-57 rep, year: 58-83 rep
• Jun 01 2012 Best nodes month 38-68 rep, year: 59-85 rep
• Jul 01 2012 Best nodes month 42-70 rep, year: 59-86 rep
• Aug 01 2012 Best nodes month 39-47 rep, year: 59-86 rep
• Sep 01 2012 Best nodes month 46-63 rep, year: 60-81 rep
• Oct 01 2012 Best nodes month 40-67 rep, year: 61-82 rep
• Nov 01 2012 Best nodes month 41-63 rep, year: 61-83 rep
• Dec 01 2012 Best nodes month 47-64 rep, year: 58-84 rep
• Dec 25 2012 Best nodes month 43-66 rep, year: 58-77 rep

• Jan 01 2013 Best nodes month 41-58 rep, year: 58-77 rep
• Jan 31 2013 Best nodes month 41-58 rep, year: 58-78 rep
• Feb 01 2013 Best nodes month 39-49 rep, year: 58-78 rep
• Mar 02 2013 Best nodes month 39-56 rep, year: 58-78 rep
• Apr 01 2013 Best nodes month 35-62 rep, year: 59-79 rep
• May 01 2013 Best nodes month 40-57 rep, year: 59-82 rep
• Jun 01 2013 Best nodes month 40-57 rep, year: 58-78 rep
• Jul 01 2013 Best nodes month 42-62 rep, year: 58-77 rep
• Aug 02 2013 Best nodes month 38-49 rep, year: 58-78 rep
• Sep 01 2013 Best nodes month 50-80 rep, year: 57-80 rep
• Oct 01 2013 Best nodes month 42-66 rep, year: 57-81 rep
• Nov 01 2013 Best nodes month 41-54 rep, year: 57-86 rep
• Dec 01 2013 Best nodes month 40-64 rep, year: 58-87 rep
• Dec 29 2013 Best nodes month 41-52 rep, year: 56-87 rep

• Jan 01 2014 Best nodes month 43-52 rep, year: 56-87 rep
• Feb 01 2014 Best nodes month 39-53 rep, year: 56-87 rep
• Mar 01 2014 Best nodes month 44-66 rep, year: 58-88 rep
• Apr 01 2014 Best nodes month 38-52 rep, year: 58-88 rep
• May 01 2014 Best nodes month 40-53 rep, year: 57-89 rep
• Jun 01 2014 Best nodes month 40-54 rep, year: 57-90 rep
• Jul 05 2014 Best nodes month 40-57 rep, year: 56-90 rep
• Aug 01 2014 Best nodes month 38-52 rep, year: 56-90 rep
• Sep 01 2014 Best nodes month 41-61 rep, year: 54-79 rep
• Oct 01 2014 Best nodes month 45-61 rep, year: 54-80 rep
• Nov 01 2014 Best nodes month 40-48 rep, year: 54-81 rep
• Dec 01 2014 Best nodes month 41-82 rep, year: 55-82 rep
• Dec 30 2014 Best nodes month 36-46 rep, year: 55-86 rep

• Jan 01 2015 Best nodes month 36-46 rep, year: 56-86 rep
• Feb 03 2015 Best nodes month 42-52 rep, year: 54-86 rep
• Mar 01 2015 Best nodes month 41-67 rep, year: 53-86 rep
• Apr 01 2015 Best nodes month 43-54 rep, year: 54-88 rep
• May 01 2015 Best nodes month 38-45 rep, year: 53-90 rep
• Jun 01 2015 Best nodes month 39-44 rep, year: 51-90 rep
• Jul 01 2015 Best nodes month 43-62 rep, year: 52-91 rep
• Aug 01 2015 Best nodes month 41-67 rep, year: 52-91 rep
• Sep 01 2015 Best nodes month 40-56 rep, year: 52-91 rep
• Oct 09 2015 Best nodes month 43-57 rep, year: 53-91 rep
• Nov 01 2015 Best nodes month 43-67 rep, year: 53-91 rep
• Dec 02 2015 Best nodes month 40-52 rep, year: 52-76 rep

• Apr 25 2016 Best nodes month 39-54 rep, year: 52-75 rep
• May 21 2016 Best nodes month 41-64 rep, year: 52-74 rep
• Aug 06 2016 Best nodes month 40-50 rep, year: 50-75 rep
• Aug 18 2016 Best nodes month 40-51 rep, year: 49-76 rep
• Oct 25 2016 Best nodes month 39-53 rep, year: 49-66 rep

• Jan 25 2017 Best nodes month 40-48 rep, year: 49-66 rep
• May 09 2017 Best nodes month 40-53 rep, year: 48-64 rep
• Nov 07 2017 Best nodes month 40-48 rep, year: 50-58 rep
• Dec 19 2017 Best nodes month 40-53 rep, year: 50-58 rep

• Jan 01 2018 Best nodes month 37-49 rep, year: 50-58 rep
• Jan 22 2018 Best nodes month 39-46 rep, year: 51-58 rep
• May 01 2018 Best nodes month 42-48 rep, year: 50-60 rep
• Jun 04 2018 Best nodes month 42-51 rep, year: 50-62 rep
• Aug 13 2018 Best nodes month 38-55 rep, year: 50-64 rep
• Sep 01 2018 Best nodes month 40-59 rep, year: 49-64 rep

• May 17 2019 Best nodes month 36-42 rep, year: 47-61 rep
• Jul 03 2019 Best nodes month 40-50 rep, year: 47-62 rep
• Aug 20 2019 Best nodes month 35-47 rep, year: 46-53 rep

• Feb 01 2020 Best nodes month 36-49 rep, year: 45-53 rep
• Apr 03 2020 Best nodes month 34-40 rep, year: 43-54 rep
• Jul 18 2020 Best nodes month 32-48 rep, year: 41-56 rep
• Sep 13 2020 Best nodes month 32-37 rep, year: 41-57 rep
• Nov 06 2020 Best nodes month 33-42 rep, year: 41-58 rep
• Dec 25 2020 Best nodes month 33-43 rep, year: 40-58 rep

• May 15 2021 Best nodes month 32-40 rep, year: 40-57 rep
• Jun 25 2021 Best nodes month 28-35 rep, year: 40-47 rep
• Jul 17 2021 Best nodes month 29-37 rep, year: 40-47 rep
• Oct 09 2021 Best nodes month 30-45 rep, year: 39-47 rep
• Dec 13 2021 Best nodes month 30-44 rep, year: 38-45 rep

• Feb 04 2022 Best nodes month 33-41 rep, year: 40-48 rep
• Mar 03 2022 Best nodes month 32-37 rep, year: 38-50 rep
• Apr 15 2022 Best nodes month 29-53 rep, year: 37-53 rep
• Jun 18 2022 Best nodes month 32-42 rep, year: 38-53 rep
• Sep 02 2022 Best nodes month 31-41 rep, year: 38-53 rep
• Nov 26 2022 Best nodes month 31-37 rep, year: 37-53 rep

• Mar 16 2023 Best nodes month 28-39 rep, year: 36-53 rep
• Mar 26 2023 Best nodes month 29-40 rep, year: 36-47 rep
• Jul 12 2023 Best nodes month 28-36 rep, year: 35-43 rep
• Oct 04 2023 Best nodes month 28-34 rep, year: 36-42 rep
• Nov 25 2023 Best nodes month 29-34 rep, year: 35-42 rep

• Jan 06 2024 Best nodes month 28-39 rep, year: 36-43 rep
• Mar 04 2024 Best nodes month 28-41 rep, year: 36-43 rep
• Mar 07 2024 Best nodes month 26-29 rep, year: 36-43 rep

Perhaps the most reliable indicator here is the lowest "best node" because the highest one often tends to be an "outlier" (that is, a freakishly popular node) while the lowest ones in the top 10 and top 20 lists tend to have similar values. The lowest best node has declined for the past four years, though the rate of decline appears to be slowing this year.