1986 Other GMC Models truck will not start

The truck starts up with no problem but will not re start after its been running for a awhile. The battery dies down and the engine will not turn over. This happens after minimal attempts. I have had this problem twice now and each time I replaced the stater. Jump starting will not work all the time. It takes awhile for the truck to charge up however I had the batteries check (2 of them) and they are fine. The last time the starter was smoking. I see smoke coming from the starter again. What is causing this. This will be the 4th starter in 3 years. What is going on. Please help. Replacing this starter agin is crazy not to mention expensive. How many will they warranty?