Bike,
The 510 connector threads on the current iStick aren't any worse than any of the many other PVs that use chromed brass connectors. They're certainly no worse than VAMOs, for instance. That may not be a sterling recommendation, but they're far better than the soft-as-butter aluminum 510 connectors on some cheap mechanicals.
When my first iStick's threads began to go "wonky"---about a month after I got it---that immediately got my attention. I immediately started exercising the same care that I do with all my other softer-metal connectors---avoiding cross-threading by making sure that the male and female threads are synced properly before screwing on a tank, using a light touch to maintain a smooth path, never forcing any tank, and not over-tightening (more than snug will short the positive pin and cause the iStick to read 0.0 ohms and not fire). That first iStick hasn't given me any thread trouble since and is still chugging along quite happily. Same is true of all my subsequent iSticks, which have no thread wonkiness at all, since I was careful with them from the start.
Maintaining the thread health on my iSticks has been no big deal---it takes just a little more mindfulness and about three seconds extra to put on a tank. That said, stainless steel connectors are much better, and I hope Eleaf uses them on all the subsequent versions, along with spring-loaded pins.
YMMV, of course.