I don't agree with the word " not possible". to be honest, free spins do not promise 100% winnings, i know that. But for some chances, you can get a lot of money from free spins feature.
I think you got the wrong side of my word bigger amount. I am not saying that you are spinning free spins for years. I was taking bigger amount in one spin.
Means you can not win a big amount in one spin. For big amount you will spin thousands of spins than you will get this. But again you will not sure about that the withdraw is possible or not.
Usually non-consistent results during free spins bonuses, the amount user can win is capped around 500x, from my personal experience. Hard to believe the house doesn't limit the winnings since the base bets are mostly less than $0.5. Imagine getting free spin bonus in most volatile slots like Tombstone Rip by NLC slot provider and hitting multiplier above 100kx. Btw max win is limited to 300kX per round in such slots, anyways imagine hitting such multi then quit gambling.
I don't really know about this that free spins are cap to certain limit only but it's logical. If there's any reported incident that a player won that amount on a free bet, then people could probably abuse these free spins especially for new accounts free spins promos as exploiter will just create multiple accounts until they hit a huge win.
Anyways, if that ever happen, the casino could just cancel these bonus as it may deem unsatisfactory on their favor and void the winnings or probably it make it harder to withdraw for that user.