Will it ruin a USB PT to keep it plugged into the comp?

Since the one I have is just a USB connector and a battery box with a Joye style battery device on the end, I don't think that there's any circuitry to control overcharging of the battery. I'd unplug it when it's not in use. You can, however, vape to your heart's content on the charged battery when it's unplugged from the computer. It makes a good longer lasting power source for those times when you need a little longer battery life than the standard 180mah 510 batteries.

The battery in the USB PT appears to me to be a standard battery made up from NiCad cells. Nicads need to be drained periodically and recharged to prevent the memory effect from occurring. If NiCads are recharged without draining fully they tend to drain faster and run out of power halfway through the full life of a charge. Draining and recharging extends the useful life of a NiCad battery.

 

Mine has been plugged in for over a month.....no problem.

If you want to unplug it after use or run the battery down to keep it alive it's probably beneficial.

I personally spend enough time fiddling with equipment, and would rather just not worry about it.

If I ruin a $5 battery that I really don't use anyway....I'm fine with that.