as another mainland bc driver, i havent washed this car for at least a month

Yes, my rear window is pretty much always filthy.

I had a different thread that I started (which I should update now) but I wasn't paying attention and backed into a not-quite-open garage door and tore my spoiler off.

It cost me - according to the BC - about a mile to the gallon in fuel economy until it was repaired.

The spoiler is your friend. Even if it does make it dirty.