Is it always better to remove the flash drive when you’re not using it, or is it mostly harmless to leave it in as long as your computer stays on?
Electronically, there’s no real reason not to keep it in the port, although you probably shouldn’t use it as a second drive as there is a limit to the number of read and writes that flash memory can support. (It’s in the thousands…)
Mechanically, however, as I know to my sorry, it’s easy to break the casing on a flash drive if, for example, it’s in the port of a laptop and you move the laptop. Similarly, if the port is one of those front-mounted ports that they have on some pc cases, the flash drive is admirably positioned to be stepped on.
NOR flash-RAM starts failing around 10,000 erase-and-write cycles (reading is free), but NOR isn’t really used in portable drives much. Most commercial flash products are built for a million. I’ve seen some higher-end produts built for eight million, and I wouldn’t be surprised if they go higher.
Leave it in if you want.