The maximum number of spins you can store is technically at 50 and you miss out on earning additional ones if you keep it at full. Typically, you would want to empty your chances away before logging out of the game and earn as much gold as you can before even checking what you have left on your island for upgrading. As there are rare chances for you to even earn additional spins past the 50 times limit, it is best to always bring it down to at least 45 so you can start earning 5 more spins every hour or so.
However, trying to empty out your attempts may not always be the best course of action to take. For once, if you already earned 3 shields to protect your island from attackers, earning an additional one would be a waste unless you have Mateys you can send it to but more importantly, getting more gold than what you can spend on island upgrades will just open up opportunities for others to take those gold coins away from you.
So for best results, be sure that you spin enough with a goal or choices of potential upgrades in mind that you can target and purchase that upgrade immediately once your spins have earned you enough gold coins. As again, there is some luck involved every time you spin the lucky wheel, exercise a bit of approximation on how many spins you need to do for you to be able to purchase the upgrade you have in mind. So for example, if you still have about 10 spins left and the cheapest upgrade available costs over 1 million gold coins and you don’t even have a hundred thousand, you might as well save those spins for later unless you don’t have shield and would be banking on the probability of getting one or a couple.