Here's a section from one of PG's Open Counseling sessions at GIT in 1988. It's a great insight into how he practiced back in the day and also something we can all learn from. I have a cleaned up transcript here and will link to the recording as well:
Paul Gilbert Practice Advice Transcript (Cleaned Up)
Q: On unmastered techniques—stuff that still needs motor skill development—would you spend like 20 minutes straight on that?
Paul: Yeah, I would spend a long time on that. That’s the good stuff. I mean, that’s the kind of practice you can do while watching TV. If there’s anything you’re going to do while your brain isn’t fully engaged, it’s motor skill work.
Now, ideally you’d pay really close attention—but for me, I’d just get incredibly bored. So to take the boredom away, I’d practice while doing something else. You just have to make sure you’re not playing it sloppily.
After you’ve gotten a few licks clean, you can usually sense intuitively if you’re playing something cleanly or not. You can tell by listening, for sure.
I’ve done a lot of that—just taking a lick and repeating it, not at the fastest tempo I can do it, but fast enough that I can repeat it for a long time.
Q: And you’d do that without thinking? While watching something?
Paul: Yeah. I mean, depending on the lick, I’d play it for 10 minutes straight just to build the coordination.
If it’s a grueling lick, maybe not that long. But a lot of stuff doesn’t take that much physical force—it’s just coordination. And for that, yeah, I’d do it a long time.
A lot of sweep picking stuff falls into that category. Like little triads—doing those for a long time won’t make your hands fall off. You could do that for 30 minutes and still feel great.
Q: So you’ve done that? Practiced a single technique for like half an hour?
Paul: Oh yeah. Maybe I’d stop for a bit to change the channel or something, but accumulated time—definitely.