Depends on my day. Much like your day today - I was worried about the storm clouds moving in and would of refused service today. It is not worth being behind for me. If I felt I was in good standing on the schedule and could of fit it in, I would of did it but of course made it worth my time.
Last Friday I mowed one because I was off and the lady's mower was in the shop. It was Bahia dustbowl and a acre at that. But the key was I was off anyway and just had a few things I had to do...they lady paid nicely ....and my wife and I had a very nice dinner out that night which cost me a hour of my time .
Like G said - try not to leave money on the table but evaluate lawns like that in a case by case.