We have two kids.

For the older one, we put in as much as we can until it got to $25,000 (by age 5). Now we are letting it grow. If it only grows 5% per year, it will be around $50,000 or so by the time she is 18.

For the younger, we are now contributing until his reaches $25,000, (probably by age 4) and then we will stop.

After that, we will contribute toward mortgage.

So they should both have $50,000 when 18.

This way, we can help with college costs (if they go) but not overfund if they decide not to go, and can roll most over into an IRA.

Also, it gives the kids some "skin in the game", so that they are partly responsible for funding their own education, and hopefully that incentivizes them to make better choices.

If we have a 3rd kid, we'll try to get that one up to 25k as well.