I currently have in place several sites using Drupal with immediate plans to do more in the near future. Because of the way I have configured my server, most of those sites have their own installations. I have thought many times about moving them all into a single installation for ease of maintenance, but I have not done so for one reason: what happens if I have a site that is using a module that gets abandoned or doesn't get upgraded in a timely manner? And with multi-sites and the potential to have several sites on a single installation (like > 20), there's a good likelihood that on a major upgrade (like from 4.6 to 4.7 or 4.7 to 5.0), I will have more than one such module.

I really see only three options: 1) don't upgrade any site until the modules are all current -- not really practical for abandoned modules, 2) uninstall the offending module(s) and live without it(them) -- also not practical if it turns out that it(they) are key to the site, and 3) upgrade and/or maintain the module(s) myself -- also not necessarily practical if we're talking several modules and free time being at a premium. I think for me the only option that makes any sense (other than not combining all the sites into a single installation, which may turn out to be the best option) is option #3. Does anyone else have any words of wisdom to offer?