To quote you Island, you said "people will work around a day".
Yes, that is true. But not many will work around THREE days.
Look, you are a new salon. You need to establish yourself. You sit here and say that you ahve enough money banked to last the slow season, so why try and cut your hours so drastically? Now is the time to show you are here to stay. Open 6-7 days a week. I dont care how much notice you give, it wont get to everyones ears. YOu are going to lose customers and potential customers. General public sees a place close more than one day a week from when they used to be open 7 and they think they are gonna close.
If you dont even know what your slowest days are on a regular basis, why chose to close on any of them?
And sorry, this is more of a customer service industry than it is a product. YOu sell a service, and that is tanning. If it was a product, then you would have to pay tax on it.
People will come to a place for the service and treatment they get. And if you run a great salon, you will always have a clean place with great lamps that tan awesome. If you just see people as a dollar sign, you will fail in the end. It is all about building relationships.