Calix's game has actaully kept a lot of pace, but that doesn't happen too often unless you get either a really good game/GM or players who are new and/or excited.
One thing I've noticed with new PbPs starting up is that sometimes there will be nothing for some time and then all of a sudden you'll get a few start up all at once.
I've had a fair few PbPs die off, so I hear ya there. Of my 34 Aliases, 31 are PbP Characters (with 2 being for a Skype game I was attempting and one my current Pen & Paper Character). Of those 31, only 6 PbPs are still active, with one about to start next week and 2 or 3 on hiatus. All of the others have folded at some point, some shortly after starting (like the one that only just died this week) and others just petered out after a longer period.
If you get the chance, take a look at any of Patrick Curtin's games. They are some of the longest still active (along with Heathy's Saltmarsh game I think). I'm in two of his, Chronicles of the Silver Rose and Tales from the City of Opal, both great fun and definately my favourites (apart from Z-Day which is on hiatus at the moment, but is the best PbP I've played in; that one was just pure luck I happened to be on to snag it as well).
Good Luck with your hunting and I hope to game with you in a PbP sometime.