Well, I'm not in the iPhone app store, but I've done mobile development before...

My advice would be to not rush to release a new app every 10-15 days, just because you have 1000 downloads a day. Instead, focus on making your next app good enough to be worthy of receiving 1,500 downloads a day, and then 2,000, etc.

Increase your install base over time with good apps.

Yeah, you can release a bunch of fast puzzle games to promote apps 4+, OR, you can just try and make better apps/games from the start.

I dunno, that's what I'm thinking. I this helps some how.