I'd say it all depends on the type of module you write (I bet you wouldn't have guessed that!).

Some modules do one thing, they do it well and there is no reason to change what they do, so once they are out and the bugs are ironed out they pretty much live their life and nobody has to maintain them any more. Case in point: Data::Dumper, current version is 2.101, released on May 1rst 1999: the interface is well-defined, the module works fine, everybody is happy.

I know I spend a lot of time (way too much according to my SO!) maintaining XML::Twig, as users ask for new features that really have to be included in the module, and as I use it in my day job. As a side note the maintenance effort does not necessarily show up on CPAN, as I release a lot of intermediate versions on my site only, waiting until I have a thouroughly tested (and complete) version to do a CPAN release.

In between those are modules like DBI, which was stable for a while (one release from june-1999 to march 2001) but went through 4 versions since then.

So basically it is up to you to figure out how much maintenance a module will need. Will it just need fixing the inevitable bugs revealed by other people using the module? Or does it look like it will have to evolve and encompass a lot more features to be really useful, or just to keep up with other modules it is based on?

If you think your code is interesting but you will not be able to maintain it you can also put it up on CPAN and explain this in the README, with your email address so potential maintainers can contact you.

And of course you should also post either the code or a dscription of the module here (an/or in a newsgroup or on a related mailing list) and listen to what people have to say about it.