GSA will have older line trucks come out for a LONG time. Forestry Department especially. They seem to keep trucks well into their 30 year old time range, sometimes as much as 50-60 years, believe it or not.
While there is a phase-out period, there are straglers that stay in the DoD system for a long time. There is a set date for termination of support, for the M35A2, that time is now past. What it means is, once that date is past, there will be no more support, parts-wise or service-wise, for that vehicle. If you turn in a M35A2 for service at a motor pool, even if it needs only a wiper blade, there is no service, only surplus. That vehicle will be replaced with something newer, like an LMTV. If a unit doesn't turn it in, or it is relegated to a base mail truck or something low-level like that, it may stay in the system a bit longer. Also, don't forget that the DoD has storage depots and little installations all over the place. It will be 20 more years before the last M35A2 comes out of inventory, because there are forgotten trucks everywhere that many don't even know exist anymore.
I read a copy of Army Reserve Magazine from 1974 once, they used to have a contest where the publisher would post a picture of some obscure MV and say "what is it," the winner would get a T-shirt or $15 or something. One month they showed a picture of a HUGE tank, is was massive. Two tracks per side. Picture was from WWII or slightly thereafter in time frame. The winner wrote in that it was a T28 heavy tank, tested toward the end of WWII, only two built, both were scrapped after testing since the military didn't need it anymore with VJ-day over. Couple months passed and another writer wrote in with a picture, a MODERN picture, showing one of the tanks beat to crap with the outboard treads removed, and said "incorrect, one still exists and here it is sitting behind some worthless shed at Ft. Belvoir last week." Ft. Knox Patton Armor Museum QUICKLY sent over a railcar and had the thing rescued. SO, just goes to show, another piece of history saved, that most didn't know was still around decades after it was "written off", so to speak.
Another few pics below, of that said tank:
T28 Super Heavy Tank - Wikipedia, the free encyclopedia
). Love to have an M-37 as my daily driver in the USA to join some parades next year (or just for the heck of it)