Also, frankly, it'd be a pain in the ass to keep it updated, or keep changing it. Domain registry costs money. It'd be annoying to have to switch to DStemp or 3dstemp or n3dstemp all the time. Perm just sounds silly, and the content is sort-of always changing so I think temp fits nicely.
it's also possible that with how the community exploded back when it hosted GBA roms and became a forum, that there's already a DStemp or 3dstemp bought up by some domain sitters, trying to hike up the prices.
Once a domain name is decided on it's easier just to stick with it. (PSX-scene is still psx-scene) And keeping the name of the site/project as the name of the domain just makes sense.