Ive put several mostly one ton drw trucks in commercial service pulling heavy GN/pintle trailer full time. This was in the '70s and '80s. They were good for 150k-200k miles before being worn out. These trucks had regular service on time. Todays same trucks are running for 500k + miles. Some over a million miles transporting RVs.
Hard to say how long a 1/2 ton truck lasts. Too many variables.
I would 'spect a 1/2 ton truck like yours that has good service and light use should go for 200k+ miles before tranny rebuild.....water pumps....front end work/etc and nickle and dime issues pop up.
