If I think I'll want to do it again I script and save it from the start. Otherwise it goes into my ksh history buffer where I have time to override that decision.

I don't agree with this premise in general. I probably rip out a dozen or two shell/awk/sed/Perl one-liners a day that are solving a very specific problem at hand that it makes no sense to abstract to take arguments, bullet proof, etc. Not all code is meant to be reusable. What's reusable is your ability to recognize and solve the problem at a meta level.

Plus I like the looks you get from neophytes when you start scripting right at the command line ...