I think the 5V or regulated 3.7V no-battery PTs are probably the longest lived PTs. Battery charging circuits in the original 510 PTs are cheap and tend to fry out. This depends on the current drawn for charging and how much you vape with it plugged in. I think the Sit and Go 510 PTs are pretty good devices, and they draw only 300 mA to charge, so ok on most USB ports.
A 5V straight-wire PT really does need to be plugged into an external AC/USB power source. It can draw over 2 amps with a regular 510 atty, and most computer/gaming USBs are rated only for 500 mA. There are stories here of motherboards frying, not just the port itself. I have been heavily using 2 5V PTs for about 6 months, and they are both running great still. Great PT for the price, but you will spend a bit more to get something to plug it into. You can get cheap 2 Amp AC/USB converters for a few dollars, but they don't live long. I got a nice 2.5 amp one from radioshack for about $20.
