Hi, I've been a Curves member for going on 2 years now, of course every franchise is different but the standard is 3x/week, 2-3 rounds depending on how many stations you have. You can work out as much as you want but the purpose of keeping a day in between is to allow your muscles to rest so that, and yes this sounds silly, they can actually form better. The intent is to use the recovery stations as just that, recovery and the machines are to be hit hard so that your intensity increases thus building muscle. What I would suggest if you want to work out 5x/week is to alternate days - 3 days weights and 2 days cardio - on weight days hit it hard, on the alternate day focus on cardio while on the recovery station and keep working the weight machines but not as heavily. Great cardio exercises for the recovery are jumping jacks, knee lifts, knee/tummy scrunches (raise hands and coordinate scrunching as you lift your knee - pretend you're pulling a bar down from above your head and meet it with your knee 1/2 way), squats and kicks - do a squat but as you come up kick out with one leg (I try to do 8 w/one and 8 w/the other).
As for rejoining fees, my Curves doesn't charge a rejoin fee if you've been away less than a year and even then they're so glad to have someone back they usually make up a "blue light special" making a big deal out of someone's return w/no rejoining fee.
Hope this helps! I started at 310 and lost 80pds, thought i was good to go, started slacking and am back at it again...170 or bust!