WW
we have one upvc window at back and it is gunky with mildew, on the seals, can't get rid of it.
Our 150yr old sashes everywhere else are going strong.
Many people don't know that there is NO NEED TO GET AN ENTIRE WINDOW REPLACED if a part of it is rotten. A window specialist will just replace the problem rail/stile on-site, for a fraction of the cost of a new sash.
They don't know this because UPVC companies propagandize to the contrary - in every local paper - targeting the old, infirm, and anxious first-generation property-owners. They've put those craftsmen out of business.
UPVC is a huge con - like selling boiler-insurance to the elderly - and one of the curses of the Thatcher years of right-to-buy.
BTW, they are even easier to get into than wood windows - you just lift the seal with a penknife, and lift out the pane. Saw a burglar doing it on some scary doc.
I really think that plastic's longevity is questionable. A friend is a museum conservator and says that they don't even bother looking at these plastics, bcs they decay so quickly - she reckoned 8-10 yrs before the process begins.
In any case, dd's plastic princess castle will last forever, but I wouldn't want it strapped to the outside of my house..