I just had my girls spayed this past thursday. I dropped my girls off at 8:30 and picked them up at 3. They got a pain shot and just curled up to me the whole night. I had the vet use disovable stitches and my girls havent bugged their stitches at all. I did ask for pain pills for after also and with hesitation they did give them to me which I did use just to be sure they were comfortable. I see no reason for them to stay overnight, especially when theyre alone. I personally would never leave them but thats just the way I am