J.T.
Hi D.! My daughter potty trained really quickly, but it took a long time before she slept through the night consistently without accidents. I'll echo what others said, my husband would take her to the bathroom before he went to bed, which gave her a chance to empty her bladder again before midnight. She never had a problem going back to sleep, actually sometimes it was a challenge getting her there! :)
I, too, got a zippered mattress cover, put a padded cover over that, and also bought the flat waterproof pads. Sometimes I would layer flat pad, fitted sheet, flat pad, fitted sheet so that if she had an accident, all I had to do was remove the top sheet and flat pad, and her bed was made for the next night. That's assuming she stayed in the middle of her bed. :) Anyway, that helped me through the frustration of washing sheets every day since I didn't have to totally strip her bed. I never let her sleep at night with her twin size quilt, just a smaller blanket over her, so that reduced the amount of laundry (quilt and fitted mattress pad usually stayed dry).
Good luck!