My car's got FinishKare 1000P topped with Pink Wax on for the winter. The FK1000p is a bit of a legend in terms of how long it lasts. People report anywhere between 3-6 months which is why it's a popular winter prep choice.
Finish Kare 1000P Hi-Temp Sealant - Clean Your Car
FinishKare 2685 - Pink Wax - Clean Your Car