Like the 5 second rule for food landing on the floor, or the 5 minute rule for leaving class when a teacher is late the 5 year rule is time frame after the wedding to have a bachelor or bachelorette party if said party didn't occur or was so lame that it isn't even worth a mention.
Married guy: Aargh! My bachelor party 4 years ago was crap... wish I could have done it properly.

Good friend: Brrrooo! 5 year rule! We throw you a bitching party this weekend! It's going to be the shit!!!

Now happily married guy: Yeeeeaaahhh!
by notsoslick January 7, 2019
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