I go by my nose first. I always trust my nose.
I always remember what my Pop said, "If there's a doubt, throw it out". I am not sure what I would do were I to hurt people with my cooking. Its just unimaginable.
Lastly, I have heard of wet aging, but never tried it and never had a problem with tender when cooked properly. Well there was this one prime rib roast but ...... I don't think anything could have helped it. Those competition cookers do a lot of stuff that only they swear by, leaving a brisket in the reefer for 2 months, might be pushing the envelope. But I have my questionable regime I did also. Go thru the butcher's stack of briskets wiggling 'em up over your head, like a big catfish. LOL You can draw a crowd... LOL
Smell it and see, then if you still have doubts, its your call.