You won't lose your credits if you quit. I quit for 4 months, came back, resubbed and imediately got 6 million credits back. Free to play will only let you have 300k or so. I have heard that some ppl have been bugged and not recieved their money after resubbing though, not sure though. Take care.
PS: Uncreative, you still owe me 300k, you're not off the hook.
-Auani