I think the fact that they issue a 10 year warranty on the material is probably the largest commentary on the durability of that material in and of itself.

I would always choose fiberglass over Fibrex and may even choose vinyl over Fibrex depending the requirements (largely aesthetic) of the client.

Is your opinion based on actual experience with Fibrex? What sorts of failures have you observed? The idea of wood-vinyl composite doesn't seem bad to me. I have examined samples and it seems to be rigid and the finish coat is quite thick, thicker even than the acrylic finish on Ultrex fiberglass products. I don't understand why it would fail any faster than fiberglass. After all, good quality wood-plastic composite decking seems to hold up beautifully. I don't mean to be argumentative, I just wondered if you have actually experienced failures in the material.

Andersen is a pretty big company with quite a few smart engineers. If the product is that good, why not issue a lifetime warranty on the frame.

I have seen quite a few examples of premature material failures in the case of the fibrex material but those are just my observations and should be taken in context of the small sample study.

I strongly disagree with the idea that fiberglass (Marvin or otherwise) will only last just as long as fibrex. The resins in fiberglass are much more UV stable than the vinyl used in fibrex and there are thousands of examples of 30 year old boats that are doing quite well in far more inhospitable conditions than a home's window placement.

Fibrex is 70% vinyl by material make-up, if that is okay, you can probably go to a 100% vinyl window and be just as good off for much cheaper.

As wow stated, Andersen provides only a 10 yr warranty on Fibrex, if this was truly am impermeable, impervious end all product that they like to advertise and claim it to be; why only a 10 yr warranty????

Regarding the 10 yr warranty, Marvin Integrity (pultruded fiberglass) windows have a 10 yr warranty, Andersen 400 series have a 10 yr warranty (25 on the glass), the Fibrex window trims, a 10 year warranty. So all 3 are comparable. The fibrex trims cost $175 for a pre-assembled, pre-finished snap on trim for a 5' x 2 1/2' window! That's why I'm interested in them.

As for fiberglass resin systems, I'm sure that the resin used in modern pultruded glass material (likely an epoxy) is far better than the polyester resins used in boat construction 25 years ago. Most 25 yo fiberglass boats stored outside in the sun their whole lives (like a window frame is) will be brittle and weak. That said I am putting Apex siding on my house with no reservations!

Marvin Infinity with a nailing flange = lifetime warranty.

I would also look at Inline.