I have two kids - a nearly 20 year old who is not the four year college type, and an 18 year old heading off to college next year.
We saved aggressively for them, and each has enough to cover 4 years at a private school if they wanted. My son did a year of trade school, but floundered and is taking some time to discover delivering pizzas is not a good choice for the long term. Because he's a little older, he had a little more in and will need far less for school - so right now, his 529 is paying her tuition until it evens out a bit (which will be about one semester).
His money is my money - and I've made it clear to him that its my money - it was saved for college, but it was also saved for him to get a start on life. So we will hang onto it until he figures out how to be a responsible grown up, and then negotiate with him based off that outcome. It might end up being used for our retirement. It might end up being used for his sister's school. Or he might decide he does want to go to college. Or he might go back to trade school. Or he might need a truck for a business, or a downpayment on a house (heck, there is enough there for a small house).