By never been upgraded do you mean that you've been putting in for upgrades when your points balance / booked fares allow and have never been upgraded or do you mean that mythical operational upgrades (OP-UP's) where you turn up at the airport and hear those magic words "dear Mr Harvyk, you'll be flying J today"
If you mean the first, well yes it can be frustrating, and I myself would never purchase a higher class fare on the off chance that I could get an upgrade through. That said they do happen from time to time, although IME, the better way is to purchase JASA's / FASA's / J awards / F awards than play the lottery as a lower status.
If you mean the second, well OP-UP's do happen from time to time (I myself had a run of good luck with them), but the airlines do everything they can to avoid being in a position where they have to give them out. So if that's what you mean by upgrades, then unless the airline gods have really smiled on you that day, they will continue to be the ever elusive. I guess if you did want to increase your chances, chose flights which are likely to have full Y cabins but empty J cabins, chose flights where every higher status pax is likely to have already booked J (IME long haul is where it's at for that), and when you turn up at the airport fully expect to be in the cabin you've paid for.