I just applied Rain X to the glass roof and mirrors (cleaned with invisible glass first) and i was wondering how long it will last before i have to reapply this stuff. It hasnt been raining lately so hopefully it stays on longer. The glass feels soo smooth after applying Rain X

 

You should expect several weeks. Whenever the water doesn't bead up as much, reapply.

 

^^^^^ What he said.

It really depends on how often you use your wiper fluid and/or
wipe down your windows with cleaner.

I redo mine every 2 weeks.

They do make Rain-X wiper fluid that coats the windshield as
you use it, but I find it stains your paint...so I ditched it.

 

1.5 week, 1 week during dusty/pollen season due to window washing fluid, but after i use up all my old fluid (2 gallons left, got it in bulk)i will start getting rainx windshield wiper fluid, and hopefully that'll eliminate that 1-1.5 week time frame

 

a couple of weeks, like everyone else said...BUT if you buy the rain-x wiper fluid it is formulated to help it last longer. Also if you do a double coating initially it will work better.