I'm not going to give specific hours as many here have given some good suggestions on that. What I will say is that it depends on a number of factors such as location, demand and trial & error. If you are located in an area with a number of other businesses open on Sundays or late Thursday nights, then it makes sense. You always want to go after the low hanging fruit and if there's a demand, you as a retailer have to fill it.
If you are a "destination location", meaning off the beaten path and in a non retail area, then it might not be worth the cost of opening on Sundays or having extended hours 12 months of the year.
I suggest to always give your prospects the opportunity to come back on a Sunday if it's more convenient, just from a customer service aspect.
Again, depending on your Geographic’s, spring and fall most likely will be your 2 busiest times and to experiment with Sundays and later hours during these peak times might be worth considering.
My 2 cents anyway...
Steve