Friend of mine has a story from 50 years ago. Guy he knew was dealing coke. Got spooked and stopped selling. Three years later he thought it'd all blown over. Set up a another deal and got popped.

Another friend that worked IT at a slaughter house said one of the bikers that worked their said, the feds aren't good at figuring you out. But when they do they never stop watching you.

There’s knowing something and building a case to prove it in court. With drugs in particular the police tend want the higher up people so will watch the others for a long time.