I get a reasonable stream of e-mails about my LaTeX packages, mainly achemso and siunitx. As a rule, I try to answer queries within a day or two, especially if I can easily provide a solution. Minor bugs tend to get done in the same time frame, with bigger bugs and feature requests sometimes needing a couple of weeks. There is the occasional “big problem” that needs more work, such as the list of issues that siunitx version 2 will hopefully deal with; these don’t really have a timescale at all, except I let people know that! I tend to keep an eye out on comp.text.tex and the LaTeX Community for questions about my packages, although often other people manage to get in first with good answers.
All of this raises the question “why”: after all, this is a hobby for me. I guess that as I’ve put a lot of work into the packages I want them to work well. So bugs, unclear documentation and new ideas all drive me to improve.