If CEE or an NO supplement permits more work in less time, heavier loads forcing a greater neuro-endo response and greater forced adaptation, then all the merrier.
... if all of those good things happen, you will be considerably farther down the path than if you didnt go the 'better fitness through chemicles' pathway, and more likely than not will be better off for having taken them even if you do discontinue the chronic admin.
The only real question I suppose is how much crap can we dump into our systems and not raise the likelyhood of cancers and/or irreperable kidney and liver damage? No one has and no one will pay the coin for double blind studies on l-analyl-glutamine-dipeptide and the like to see how it affects HEALTHY people, so we will never know the payload of some of the crap that gets sold in 'healthfood' stores. There are NO laws that regulate how much Unidentifiable Matter you are permitted to have in dietary supplements. That coupled with the fact that almost all the raw powders come from factories in china, give me the shakes from the get go. If you can find a supp company willing to give you a copy of the assays of their raw product? BUY FROM THEM! (Anafit is one I know of, I dont know any others...)
If you took all the performance enhancers available over that counter that had anecdotal evidence of increasing output or recovery, you wouldnt have any room left for food! You just have to consider risk/reward, i guess.