I had a deep cleaning done. I hadn't been to the dentist in over 20 years. They numb you and do half your mouth at a time so it was two visits about a week apart to have it done. I wouldn't bother with it if you go to the dentist regularly. I did it because it really did need to be done. They've never suggested it since. I got cleanings every 4 months for the first 2 years after the deep clean but I've changed them to every 6 even though my dentist wanted me to stay on the 4 supposedly since it had originally been so long. I'm not a fan of tooth stuff so going every six months is more than enough for me.
I have a single cavity in a wisdom tooth, currently, that when I go in for my cleaning in Jan I'll make an appointment to get filled. The dentist didn't fill it last time I was in because I hadn't decided if I was going to get the wisdoms yanked. I'm not in the mood to deal with it at least not for a few years so I figure I'll just have it filled.