Some F.T.'s are more durable than others. The dri ducks stuff is the really thin, smooth material. If babied, and not subjected to abrasion from branches, thorns, etc. it will last longer–tyvek tape is really good for it for when it does get holes. The thicker, more fuzzy stuff is a little more durable in general.
MOst of the F.T.'s is all or mostly polypropylene and like MB said, doesn't need any DWR, because polypropylene is so innately hydrophobic. I have noticed that PP does absorb oils easily, so keep it away from oily stuff. A front load washer, on delicate with gentle cleansers like atsko, then hung dry is best.
There is a relatively new kind of Frogg Toggs out there called the Toadz line. It has an outer layer of densely woven polyester.
It's much tougher and more durable than the other stuff, but also noticeably heavier. It may require a DWR, but i'm not sure about that. I'm not sure how the breathability compares to the more classic forms.
It would be really interesting if a company decided to combine the cheaper, common, very light, ultra hydrophobic, but less durable PP materials with UHMWPE fiber materials which are very strong, durable, and also quite hydrophobic and pretty light (dyneema, spectra, etc).