I have a file I call
Packages.tex that I put all the macros I use for a generic document in.
I've found that this file gets rather bloated, and when I do remove elements of it I don't use anymore, it will cause compilation errors on my previous documents. Usually at that point I only care about the .pdf so this isn't an issue, but it'd be nice to have a better option that leaves me with a .tex file that compiles well, without either having a bloated Packages.tex or having to resort to having multiple versions of it (so Packagesv1.tex, Packagesv2.tex, etc).
Does anybody have a good solution for managing an evolving file of macros with past documents?