IF you buy a 3510 my guess is you will NEVER use that 310 again. When I bought my 352 before the 3510 was created, I had a 310. It had a muffler mod and tuned correctly. That little thing Cuts great BUT, it was just sitting unused. Almost new. I sold it to a friend for 130 bucks. They use it very little. I keep it up for them and sharpen the chain etc..BUT.. I would never buy another 310.. I'm 75 now and use my saws less so I'm happy with the 352 but a friend bought the 3510 and it's awesome.. I have the 490 and use it some. I'd bet the 4910 is nicer.. FOR most of what I do now the 490, and the 352 are the most used saws. For that OCCASIONAL huge tree, the cs590 with a 28 inch bar does the trick..All of my saws are cranked pretty often even if I am not going to use them. Every gas engine on the farm is started every couple of months just to keep them alive..For that I use NON-ethanol gas and One Ounce of Sea foam to a gallon. I add just a TINY bit of Mixed gas to the Chainsaws. Crank them warm them up and then empty the fuel out while they are running. I then let them idle until they die. Some folks say differently. It might allow the carb parts to dry out. It might be worse. But that how I do it.. I once got a saw from a guy that had set up for 5 or 6 years. BEFORE I did anything I removed the Carb and soaked it for a month in a jar of NON Mixed gasoline. THEN I cleaned the carb. That way the internal gaskets were soft and DID NOT crack..But,, what do I know? It's just my way. Yours might differ..