The lifespan varies on these trucks as much as any other vehicle. With that said, it's not uncommon for the military to sell them at 30k to 60k miles and as long as you do regular maintenance they should last at least twice as long. Not too many people drive them on a daily basis so I only know a couple people that have over 100K miles on them. The bodies usually rust out long before that. (Lousy rustproofing)
Insurance is a tricky one. As long as you don't haul anything in it, you can get collector plates and use collector vehicle insurance. That's what I do through an insurance company called
Traveller's Insurance. Though you need to contact a local office since they won't have a listing for an M35A2 on their website. A local agent will need pictures, registration and what not before getting it insured. I pay a little under $200 a year for full coverage collector vehicle insurance. It's cheap because they know I won't be using it much because of the collector license plate restrictions.
If you want to license it and use it for work or hauling, expect to pay a lot. Here in Washington state you have to pay tonnage when you buy your license plates. On a truck that has an empty weight of 14,000lbs and is designed to haul 24,000lbs on the highway, it will cost a lot. Insurance for the truck is comparable. Insurance companies are expecting you to haul heavy loads and will charge you a comparable rate.
CDL is not required! (Unless you live in California, those communists) Even though the truck has air over hydraulic brakes, you don't need a CDL because its GWV is under 26,000lbs. With that said, I do have a class-A CDL. I want to get this truck a bigger brother some day.