I'm a one-man, mobile-only business handling both business and residential clients. I work out of my house with a business phone number separate from the home number. I'll answer the business phone just about anytime (within reason) -- hey, always looking for an opportunity to book an appointment!
However, I try to schedule calls only Mon-Fri. Will do an occasional Saturday call, but never do calls on Sunday.
I have a good reciprocal working relationship with two shops here in town.
Shop 1 is open Mon-Fri 9-5:30; and Sat 9-2.
Shop 2 is open Mon-Sat from 9-1pm and 3pm-6pm. He uses 1pm-3pm for "lunch", errands, etc. (Not sure how he gets away with this, but it works for him.)