I have 3 iStick 20s still in service for out and about. Granted, one the 510 is finally failing, won't keep the ego adapter in place (always usef with the 510 to ego adapter). Another the 510 is failing - have to nudge the 510 pin up occasionally (also always use the 510 to ego connector), but this one doesn't hold it's watt settings either. 3rd is just fine. 3 Defenders, 1 25 watt and 2 36 watt, still going strong. Even use the Defenders for 510 tanks.
The 20 w iSticks are almost 2 years old. Not daily use, but when I travel (for work, which is often) I use them and my Defenders for out and about almost exclusively. I love them.
In the past year I have concentrated on external battery mods and I have a good supply, but when these babies die they will be truely missed. I do have 2 30w iSticks in my backup that I exercise from time to time to make sure they are still healthy. I use my ego threaded toppers on them, so handy for pocket storage.
Old tech just works for me.