the functional lifetime of UV filter film for home windows

Factual Questions
1

Back in 1992 my father had our home’s big southeast facing windows coated on the inside with a plastic-type adhesive transparent film with a bit of a tint to it, which was advertised as filtering out the UV rays which would fade the furniture, etc.

It seemed to do its job adequately, and still seems to be doing so. It’s not peeled away, become discolored, or had any noted change in effectiveness (not that we’d necessarily notice).

But as my wife is now redecorating the place (which we took over back in 1995) she wonders if the film needs replacing. We’ve no idea what the film is called, made of, made by, etc.

I’d rather avoid it if possible, but if it does become less effective at blocking the sun’s UV rays, I suppose we should consider replacing/upgrading.

Anyone have info on whether this general sort of material from circa 1992 had any loss of ability to filter UV over time?

2

I was only 4 in 1992 so bear with me. During various jobs (construction rehab type/handyman) I/we came across a lot of them and never replaced them if they were intact/corners not peeling back and the window was double paned (unless requested/whole replacements). The reason for this is the material is in itself fine, it is made in such a way that it will resist damage from the sun and therefore what passes through it. A test I heard from one of my fellow workers was that if you can store a bottle of beer in front of it for a day (sunny) without it getting really skunked, they work fine. Personally though, I have OCD tendencies and like to re-do things and keep things update, so I probably would replace them anyway, due to age. But thats me. If the furniture hasn’t faded after all these years, or at least not very much, then leave them in.