I shoot in the basement almost daily. I do try to get outside on the weekends (I am not at home during daylight) and I shoot inside at ranges 1-3 times per week.
I didn't do so hot last night at the indoor league. I think it's because I didn't practice all last week because I was out of town then went to K-zoo and shot a bunch of other bows.
So, tonight, I went down to the bag at point blank range and focused on form. I extended out to 5 yards for a bit. I will hit the range on Thursday and the outdoors this weekend.
Form work is great in the basement. Plus, if you have a spring turkey season you can work on up close seated shots.