"Reinventing the wheel" is more often than not a remider that a wheel exists and as such meant to give you a chance to examine the existing wheels (you may not have known about) and see whether you really do want to spend time building your own. It might be the case that you know the old wheels and for whatever reason important enough to you, you decided to build a new one. It might, and quite often is, the case that you simply were not aware of the old wheels and one of them fits your needs perfectly. And it might be the case that reexamining the suggested wheels will improve the design of your new one.

Yes, the time is yours to use as you wish, most of the "you are reinventing the wheel" posts just try to help you make an informed decision.

Reinventing the wheel because you want to learn is good. Reinventing the wheel because all available wheels are suboptimal for your needs is fine as well. It's reinventing wheels because you did not know the old wheels that's a waste of time.