All the time. A proper good tank is an assemblage of balanced factors that never really go out of style. This is a centurion, first introduced in 1945:
The gun, powerplant, gearbox, hydraulics, etc. are excellent. It serves well as medium tank today. If you do not need a heavy main battle tank, this will do very well.
Shermans, Leopards I, etc. are still fine machines, especially with retrofits.
M113’s are still in use all over:
A metal box was put on a good engine and gearbox that first saw service in 1960. It was a platform for whatever you wanted it to be. It remains an excellent vehicle for certain applications.
The AMX 30 is well over 55 years old and recently mustered out French service:
The French do a thriving business cleaning them up, retrofitting them and selling them.