Lots of good sealants can make it for four months through winter. The trick is finding one at a reasonable price. I can vouch for Collinite 476 paste wax. It will definitely make it through, In fact, its kind of hard to take off even if you want to. Collinite is also very shiny all by itself. You can bling it up by spritzing it with Duragloss Aquawax after a wash. The only bad thing I have to say about it is that you have to mail order it most places.
The Duragloss combination (you add a hardner to the sealant) is reputedly tough as nails. Not too expensive. Duragloss is sometimes available at NAPA or Carquest.
I had luck with the Jetseal 109 product, but its kind of expensive (although easy to use). As I said, the trick isn't finding a good durable sealant, the trick is finding one at a good price.