In time when I was working on Wammu 0.18, I realized, that making release not very often is bad thing. You usually get same reports over the development period and telling people that you have fixed it, but not yet in any released version, doesn't make them happy.
As you can see from past weeks, I switched to making releases as often as possible. I will try to add new features quickly after release and then give the code some time for stabilisation (well, this would need a bit more testers than I currently have). I'd like to avoid delay longer than month between releases, if there is something to release (I doubt there will be any major changes in python-gammu in near future).