I am a bit OCD when it comes to car cleaning but I think it is easy to get sucked in by all the hype around the vast array of products on sale these days. The car detailing scene takes car cleaning to levels that means a simple wash can now take hours. They often start with an all purpose cleaner, jet wash that off, then snow foam, jet wash that off, then shampoo with a 2 bucket method, then jet wash again, then dry with a microfibre towel and finish off with a quick detailer.
Waxing and polishing then follow. First they clay bar the car, then rinse and dry again, then they will polish and, after that, they will then apply a sealer or a carnauba wax.
It's a harmless enough hobby (although you could question the use of water) but is it all necessary?
To answer the question though, what I have gleaned is that sealants usually last a fair bit longer than wax. However, the Bilt Hamber Double Speed wax mentioned by Jocko has both wax and polymers in it and lasts ages and ages. I bung it on every six months or so.