Viair, there is a reason they sell a rebuild kit next to all the ads for these. Alright, sorry for being a smart ass but there are way to may stories for having to rebuild the AZ compaired to a Viair.
You must have your pressure under 150 because anything over that pulls the life span down to about a year.Even then they don't burn up they just don't pump a whole lot.I used the thomas compressors for many years before the viars where known and have rebuilt more than most people have had hot meals.I even learned what parts where interchangable and what models hade the big motor.I bet I still have a box of spare parts in my back room.Ill have to throw them away next time I go back there.With that said I havn't used or even seen a thomas in years so they might be different now.As for the zenith I can't afford to have compressors going out on customer rides so I won't use them until they have a provin track record and the price comes down.
I used to have two viar 380s on a five gallon tank for 2 years. never a problem. now I have one airzenith on a 5 gallon and it is faster, pulls less amp then two viar