Eh, leads to "unfixed bugs"? A bug can only be fixed if there's a release - no release implies no bug fix (a bug isn't fixed if the fix only lives in a source repository).
If you release four times a year, there are four releases a year that can fix your bug. You know when the deadlines for the code freeze are, and anyone can anticipate on the code freeze by sending in their patches early. With releases on unknown times, even if "frequent", there will always be this new patch to be added, fixing one bug, opening another. And another. And another. Just witness Perl development for the past 5 years.
I'd say, the best thing that happened to Perl in the past five years was Nicolas decision to do frequent, regular releases. Too bad it's already slipping.