I love my Flips (I have mostly SD) but I sometimes use the insert with other wraps - if they are close-fitting enough they work fine. I use Motherease Airflow, and with his usual nappies he needs a Large but with just an insert a Medium fits ok. I believe Motherease Rikki (the aplix ones) are even better. I also know of people who use Flip inserts in a BumGenius pocket (they fit the V4s perfectly).
I have 3-4 days' worth of nappies and find that it's not winter that's the problem with getting them dry (and half my stash is bamboo fitted), it's autumn and spring, when it's too warm for the heating to be on but not warm enough to air dry quickly. Winter I put my bamboo nappies on a rack in front of the radiator and they take 1-2 days. When they air dry without a radiator it might be 3 days. I wash every third day so I am usually putting a fresh load in at the same time as putting the last, only just dry, load away.
I have about 25 nappies I think. But we don't use cloth overnight at the moment, so we get through 3-5 a day.