I struggle with this as well. My business mind says I should be open but....
I was open on Saturdays from 9 - 1 for 3 years. Some Saturdays were good and some were not (If I did not work those Saturdays were usually not so good). When I started closing on Saturdays my gross sales did not go down. I felt that since I was losing 4 hours on Saturday I would extend my hours during the week 4 hours so that is how I ended up open late for two evenings. It has taken awhile for it to catch on but I do get some business by being there late. Even if no work comes in after 5 it allows us 2 nights a week to get other work out so these days can be more productive. I definitely like this schedule better than working weekends.
I do have competition open on Saturday. Tire stores, Walmart, Sears, Ford dealer, Honda Dealer, Toyota Dealer, Express Oil Change and others. I might possibly go back to a Saturday schedule when my kids get a little older but right now I enjoy the time off and if I can make enough during 5 days I plan to keep it that way. My emplyees are much happier not working Saturdays and most customers will schedule during the week. We try to make it as easy as possible with free shuttle service or even a free rental or low cost rental depending on the service.
You have to draw the line somewhere we could be open 24 hours a day.