well, the answer is it will take decades, there are plenty of high mileage old vehicles around with perfectly good original pvc wiring, I have some of them .... as I said, it's your money, if you think you need the most expensive materials, go for it, or use some PEX tubing for conduit for the same protection you think is needed
there is no such thing as "PEX wire", PEX [polyethylene, cross linked] or XLPE [cross-linked polyethylene] is the plastic, that's why they call it XL wire - and yes, as stated in that article, cross-linked polyethylene has been used for quite awhile as the insulation of choice for high voltage applications, I suspect you'd find it's on most modern battery and welding cables
Bill
