Tā zǎonián de chéngjì zài hǎo, xiànzài yě bù néng yìzhí chī lǎoběn.
However impressive his early achievements, he can't keep living off them forever.
Tips
usage
Typically negative, implying laziness or complacency. 老本 originally means capital / principal (as opposed to earnings) — you're eating into your savings instead of making new ones.