Here's how I learned a lesson about not deviating on the front end in the winter, unless you have to.
I had a deadhead to EWR, I happened to coincidentally be in Memphis, but I deviated anyways. I figured I'd go out early in the morning instead of late in the evening.....nicer to get upgraded on Delta than fly a USAir commuter flight, that's for sure. The scheduled flight was the last one of the night, really poor planning by the company.
Some talk about possible snow on the east coast, not a big deal, but I was going through ATL in the morning, tons of backups to several airports in the area, no risk, I thought. After I landed in ATL, my flight was cancelled, and EVERYTHING was cancelled to the east coast. Finally found one flight to my destination that was two hours late, but still going, and boarding, right then. Frantically ran across the terminal to the gate, begged for a ride, everything full. At the last moment, they said they had a jumpseat. The captain was getting an IOE and he was a real dick about it, but let me ride. Taxi barely made it to the hotel because of all the snow.
The fo never made it, his trip was cancelled, because he deviated. They pulled someone off another EWR trip to fill it, and might not have found a captain, had I not made it.
So what did I gain for going through this stress? A couple of Delta miles? Yep. Appreciation from the company for my effort? Uh, no (I wouldn't expect that for just doing my job, however). Working for a couple of days instead of getting paid for going home? Yep. Stupid, stupid! I hope I don't forget this.