I say it depends on the ages. A girl at my school (16) was dating a 37 year old. They had sex when she was still 15 which is not the age of consent and now he's in jail. Honestly, just make sure it's all legal. And I personally feel anything more than 7-10 years is too much. 10 is pushing it, but it's not too bad.

The rule of thumb is the half his age plus 7. Say he's 20, half his age plus 7 is 17, so any girl younger than 17 is weird and wrong. If he's 22, younger than 18 is wrong., 24 he should date 19 or higher.