I noticed a lot of people here had to regain all their badges, is that optional, forced, or just good practice? (so it's easier to find bugs?)
It depends on what you're comfortable with. If you rarely ever get to play and only barely managed to unlock everything, there's a lot more at stake if you start again from scratch. If you can get said unlockables in a couple of games, I imagine this is less important. With the exception of recent months (and only because I'm really short on time these days) I always rebooted from version to version. However, in my particular case, the value of achievements has also grown to the point of insignificance in recent months, what with being a developer an' all, so it's not really a big deal for me: I don't even post my stats here anymore.
Some of it has to do with exactly how much changes from version to version. The difference between 0.9.9.4 and 0.9.9.5 is quite large when it comes to badges, which alone will motivate a lot of players to retry with the new requirements. There's also the matter of rebalancing in enemy AI, equipment, levels, stats...practically every time a new version has come out (at least since achievements have been around) there has been enough that has changed to believe that getting said achievements is a very different story. The same will be true of 0.9.9.6.
While I'm at it, how often do new versions come on average?
We can look at the Announcements forum and track the release posts:
DoomRL 0.9.9.5 has been RELEASED!
DoomRL 0.9.9.4 has been released!
DoomRL 0.9.9.3 has been released!
DoomRL 0.9.9.2 has been released!
The DoomRL 0.9.9.1 has finally been released!
The long awaited DoomRL 0.9.9 has finally been released!
Ladies and Gentlemen,
So, recently we've seen them come out every few months: prior to 0.9.9.2, however, you can see that it becomes less regular. DoomRL 0.9.9.6 is slated for March (April at the latest, probably), and Kornel has said that he wants to release something within 4 months from now on (and he's basically managed to keep to that).
Really though, I'd like to try and either change or remove aspects of the unlocking part of the game, which gives people a lot more of an incentive to change files from version to version. We still need to talk more about it.