How old is too old?

While lunching with Bianca today we started talking about age limits with dating. How low and high would you go? Even though I'm not in a position to date it's fun to discuss. My upper age limit would be 15 years- that would be a 40 year old guy (any older and it would be too much like a father figure), my lower age limit would be 5 years- say a 20 year old guy. Bianca was much more open and would be willing to go to I think 25 years upper but only 5 years lower (correct me if I'm wrong Bianca- I have a mind like a sieve). There is a problem with this logic though, if you set these limits you need to be certain of ages when you meet people. I suck at this and can't pick ages even in a 5 year radius. Just this year has the id checks stopped for me- it's only taken 7 years to look 18. The boy is the same- he turned 30 today but is in denial. Up until only 2 years ago did he stop getting carded.