401k需要每年都放吗？
Yes, because this is one of few delay tax benefit US government allows. If you have company matching, that is your free money.
现在45岁，
You are too young to retire or too poor to retire.
里面多少钱以后就不用再放钱进去了？
This is a dumb question. How much is too much?
问这个问题的原因是听说401k65岁以后才能取，
You can withdraw anytime. Before 59.5, there is a panelty. After 59.5, it is ordinary income. But there is a IRS rule which allows you to withdraw at 55, you have to follow the rule, otherwise, there is a panelty.
里面钱再多
Another dumb comment, I have never heard that someone worries about too much money.
