As a rule of thumb, if you're re-applying, you need to send out more apps. Apps are cheap, it's the interviews that are expensive. If you have to reapply to IM you should probably be applying to 50-100 programs (and don't waste your money on the big names) unless you failed Step 2 last year and this year improved it to a 99.
To actually answer the ? you asked though, invites go out anywhere from now to early Jan. If you don't have a dozen or so invites by mid November you need to apply more broadly.