It should hold up just fine. The Comp M’s were .Mil issue for a LONG time. They were a pretty good sight for their time, but Aimpoint has really improved upon them as of late (M4, Micro).
I also run a 8-9 year old comp M XD on my backup AR. It is still going strong and holds a zero. FWIW much of its life was spent on a 7.62x51 H&K that was shot frequently.