I would say playing the Gilbert 3NPS stuff at 120 sixteenth note triplets would be a good goal. It is a goal I use for most of my students who want to play that kind of stuff. 12 notes a second is quite easy to attain, progress usually slows a lot after that. Really it depends entirely on what...
In short bursts yes. I got comfortable at about 265 and could apply it with simple 3NPS runs. 280 was just on a single string. It was a good experience though and it made slower tempos like 200 seem effortless.