"If it quits snowing at 5am and all of your customers need to be plowed by 6am; can you get them all done? "
My commercials are all promised completion times, but no promises are made for residentials, it could be 5 am or 8 pm, its the same way with most of the residential plowing guys that I know of. Standard clause for my commercial accounts: "Lot to be cleared by X am Mon-Sat, unless storm still in progress, then a path will be kept clear thruout the day."
Promising completion times for a $40 account just doesnt seem like it could be profitable if you have to be running around, and limiting your number of clients. Avoid it if possible.