Ughh here we go again....
I'm surprised to get this question from you, given your vast knowledge of the window industry as a whole.
I'm on mobile so this reply will be limited, but look up the study by The Georgia Institute of technology " Life Cycle Assesment case study of north american residential windows"
A more recent study from the Freedonia Group (2019) which states that Fiberglass windows have the longest expected lifespan
Or, get your hands on the Government released "The Consumer's guide to buying Energy Efficient Windows and Doors" by Natural Resources of Canada (Im sure ya'll have these in your showrooms)
It's really not rocket science. Fiberglass expands and contracts (coeficient of expansion) 8 TIMES less than vinyl. It is also 8 TIMES stronger than vinyl. These all lead to a window that lasts approx 40% longer over its liefspan. Less sagging. Less warping. Less movement in the frames period.
(This is just scratching the surface. And we're not even talking about the Aesthetic benefits)
I do this every day, just like you Jerico, and I cannot tell you how many vinyl windows I replace that are under 12 years old. Wether the casement has sagged under its own weight, or whether a slider no longer slides, or a double hung leaking air like a sieve because the frame has warped. I don't need to read a study. I see it everyday. And honestly, I feel bad for these homeowners
Should the price be double, I would be the FIRST person to buy vinyl windows for my house. But given a reasonable quote, there's no doubt Fiberglass offers a vastly superior window/door framing material. Especially as window sizes get larger and larger
Can't wait to see what happens to the Vinyl window industry when everything goes Triple Glazed in a year or two.