In college I had about 4 years of no cleanings, drank like a fish, and probably brushed just once a day. I'm curious what's everyone's age and how many fillings/ how much dental work have you had done? I'm 38 and have 6 fillings, but based on what the dentist says I'm probably ready for another 6. They seem to want to fill anything that isn't a perfect tooth.
No, they want to fill cavities while they're small because cavities are like rust, they will eat away at your tooth until you need very expensive work or the whole thing replaced.
Also, some people are more prone to gum disease while others are more prone to cavities. They are very different bacteria, so when someone brags that they never floss and have never had a cavity, chances are their structural bone that holds their teeth in their skull is dissolving steadily and their teeth will literally fall out of their head starting in their late midlife depending on how negligent they are.
Either due to cavities or gum disease, very few seniors have their original teeth despite in most cases this being entirely preventable.
It's not unusual for seniors to spend several tens of thousands on dental care as the years of neglect build up and cumulate in more and more expensive care, because contrary to popular opinion, simple dentures aren't actually a reasonable option. So $60-100K treatment plans are very common.
It's possible your dentist is over treating and a quick second opinion could clarify that, but if you've already had 6 cavities by 38, I would say that another 6 at this point is reasonable, and I would expect to get many more moving forward.
Because guess what? Getting a filling makes you MORE likely to get another cavity, not less. They have a lifespan and are FAR more susceptible to reinfection than virgin tooth is.
So if the conditions of your mouth were such that a pristine tooth could get eroded enough to need a filling and nothing changes, you are absolutely guaranteed to keep getting cavities and the rate at which you get them will snowball, and the damage to your tooth with get worse and worse each time.
Most teeth with fillings are destined to eventually need crowns if nothing in the oral environment changes to lower the rate of infection.
So the question isn't "how many cavities are normal for my age" the question is "how do I stop getting these cavities?" And if your dentist doesn't have a clear answer for that, get a better dentist.
Source: I've been a consultant for medical a dental clinics for years, it's my job to know the economics of individual patient disease patterns. For an average person who doesn't engage in enough preventive care, I can expect to get around $100K worth of preventable dental work out of them if they can afford it over time.