"Last Vegas" is the geriatric version of "The Hangover". Still funny, not that crazy and a little bit romantic too.
To make a long story short: before meeting his life time friends in Vegas, 60+ Rob gets permission to cheat in order to revive his marriage. But when he is in bed with a young girl he can't and explains:
I hope there are men thinking the same in real life too.
A quote a day keeps the doctor away!
P.S. other interesting quotes on marriage from Elementary and Pride and Prejudice