Being at the "wrong FBO" is my favorite. My trip sheet and the broker say Atlantic, you bet I'm there.

In my 7 years of experience, so far it has been anywhere from 5 minutes to 4 hours.

Bottom of the barrel charter job: up to 5 hours
Better charter job: rarely more than an hour
Last 91 job: half hour early to 2 hours late, never a call.
Current 91 job. 30 min early, always a call 15 min out.

I like the guy I work for currently

This is corporate aviation, we exist to help the PAX succeed and/or to provide them a safe, comfortable experience that THEY are paying for. They are never late, you are just ready early. They, or their peeps should be made aware of any timing issues well prior to the flight. If you then miss a slot, run out of crew rest, etc... you politely explain what happened and what options you are working on to get them on their way.