A long drawn out question but it’s bugging the **** out of me.

I thought that I would put 1-2 inch of mineral wool and then fiberglass behind it but what is the difference fiber glass is made from spinning grains of glass beads at just over 2000 degrees f. mineral wool is made in the same process using Iron slag and basalt rock at approx 2800 degrees f. both use formaldehyde binders in the glue holding the weaves together, both have a melting temp well over 1500 degrees f. which is probably 3 times temp I would ever bake anything.

So, Here is the question.

Why the he!! would I pay 2-3 times as much for mineral wool that is almost impossible to find locally?

I know a lot of the guys here use fiber glass. If you do how long have you had your ovens in service and how are they holding up?
Thanks