Re: my back windows always full of condensation
I would set out bits of newspaper to try and find where any water is coming from before replacing any seals.
If the window is always full of condensation, first place I would be looking is the footwells. See if any of them are damp (or soaking), usually not easily spotted if the leak isn't too bad, as the water hides under the mats. Does the car smell damp at all?
It's a common problem as you'll see if you do a search for "wet footwells" on this forum.