Fascinating; how come I've never heard of this? It seems like the sort of thing dentists would advertise.
I had this done during youth, never had it reapplied since, and so far, now heading towards my mid-thirties, never had an issue with my teeth. And, of course, I regularly brush my teeth about once or twice a day.
My dentist checks once a year to see how far the sealant has worn off. I could get it reapplied if necessary but not for free this time. I'll strongly consider paying up though when faced with the choice since this treatment worked out very well for me.
The only thing a dentist can give you that actually lasts a lifetime is a gold crown. Everything else needs to be fixed at least once in a decade.
For everyone else, it doesn't help with cavities between the teeth where a lot of people get cavities. The sealants just sit on the upper side of the tooth.