Many years ago (more years than I would like to admit), my brother and I bought up a bunch of used 3D targets from an archery shop that was replacing and upgrading their targets. We got 15 targets for about $200. They where in rough shape. We bought up some foam mix kits in Black and Tan...and went to work on them. We used the mix and pour foam to repair them for years, rather than buy inserts. These “worn out” targets lasted us close to 10 years of pretty regular use before we scrapped them.
3D targets can last a while if you keep repairing them...keep the sun off them (ours were set up in the woods), keep them out of the elements as much as you can (we up them up in the barn during Fall/winter)..and if faded, less than picture perfect targets are acceptable.