convertible plastic window maintenance

[bdup@xxxxxxxxxxxxxx]

i just got a new rear window for my 95 325i convertible. it was by no means
inexpensive, but i'm amazed at how clear it is. i swear i don't remember it
being this clear when it was new.  how long should i expect it to last (5
years is probably too long between changes) and what's the best way to keep
it nice for as long as possible

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