How long before replacing injectors on CAT 3406 / 3408?

My 3408B has done 689,000 kms / 430,625 miles / 10,042 hours since last fuel injector / pump element change. I've used fuel additive on every fill. I'm just about to check valve lash, so I'm wondering if this is a good time to change the injectors? It's still getting good fuel mileage. Injector # OR 3422. Any CAT experts care to comment?

 

It's definitely pre-emissions lol
Also the additive gets rid of water and algae which is an injector killer, and helps with smoke.

 

It's the pencil injector. It was originally a 3408A but at the last in-frame CAT changed the injectors to 3408B with adapters which are genuine CAT as far as I can make out. Had to change injector lines and valve covers as well, so it is effectively a B engine.
I've run it out of fuel twice under heavy load because I forgot to turn on the fuel crossover taps on the fuel tanks which is a worry because that won't do the pump and injectors any good.

 

Maybe I'll wait. I'm a bit stuck for time atm. I'll still check valve lash tomorrow though. My weights are always around 176,000 lb when we're hauling steel like I'm going to be doing for the next 6 weeks.

 

I rang CAT and they said $100 to test. I imagine that's 100 each. New or reman aren't that dear on the mech engines, but so far this weekend I haven't been able to get a price on the CAT SIS system because my engine number doesn't match my updated injectors.