Cheers Mick. I've had a good look through it in total darkness, the reticule is still visible though it isn't bright as the tritium has decayed over time but still usable. Obviously this happens to all sights that use tritium including the susat, so that didn't surprise me for a used acog that's a few years old.

On a yank forum I saw where someone had got round this by using black masking tape to stick a mini led keyring torch to the fibre optic rod to make the reticule bright again. Ugly, but worked.