This is sometimes possible but generally on Microgaming tournaments when you buy credits, which are then variable to bet – you must spend them within the time limit allowed for those credits (as well as the time limit for the whole tourney itself).
Where you have bought a fixed number of spins (when every spin placed will be for exactly the same value also), for example on many NetEnt – you can quit the game and go back in later (obviously the time limit for the whole tournament will still exist to so be careful not to go over that).
On some, when you reach zero or the time limit for that number most recent buy-in (or re-buy) – you may be given a time limit within which you must get your re-buy or otherwise your participation will be considered complete.Also, check the last re-buy time available (often this will be some time before the end – so that everyone making a rebuy late on has a good chance to score (win credits) with their new spins / time bought.
