Yeah, it's cool when you can pull one off. I think I've only gotten one 2 or 3 times, even though I go for them a lot. When guys get in my open guard, I instinctively go for that spin-under knee bar; I really should drill other open guard moves more. It's cool when you can actually get them.
If you feel like you're good at knee bars, drill them some more. Get good at those. You want to be well-versed in submissions, but you need bread-and-butter moves for competition. The thing I've noticed is that when you think your go-to moves aren't working anymore, it's usually because guys in the gym are getting used to how you roll. Work on creating more setups for those moves, but don't give up on them.
Example: My go-to moves, in the past, have typically been triangle choke, toehold, rear naked choke, and armbar from mount. Before, it was rare for me to get submissions from any other move (except heel hooks). In the gym, guys KNEW I was going for triangle chokes, and they knew as soon as I started touching their legs, I was going for a toehold (what I love about the toehold is, like the kimura, it can be done from almost any position). So a lot of the time, they'd defend it. I would think, shit, I used to get that move all the time, why isn't it working anymore?
My first ever competition, I went 4-1 for the day, competing in 2 divisions. (The picture in my avatar is me in that competition). The 4 fights that I won, I finished by submissions. Wanna guess which ones? Rear naked choke, armbar from mount, toehold, triangle choke, respectively. If you have those fall-back moves, then when you try new stuff, at least you have something to go to.
The entire point behind this post wasn't to toot my own horn (I really need to get in more competition anyways), but to make a point that if you find you're naturally good at something, you do want to strengthen your weak areas, but improve that strong area, too. I've always found I'm naturally good at leglocks for some reason. I was hitting them when I only knew extremely basic (sometimes incorrect) methods of hitting leglocks. Now that I've actually been studying them, and learning good setups, my leglocks are becoming unstoppable. You hit a kneebar on an upper belt. That's a tough move to hit. If you like kneebars, learn more about them. Study set-ups, study flow moves.
In fact, Stephan Kesting sells an awesome DVD on kneebars.
http://www.grapplearts.com/Kneebar-Info.htm
I hear lots of good things about it. The cool thing with kneebars is that there's so many transitions to them and between them. If you can master the toehold, the heelhook in your neck, the kneebar, and the knee pinch, right there is an unstoppable lockflow once you grab onto someone's leg.
Awesome lock flow for legs that everyone should know:
1) Fall "back" (really to your side) for a footlock/achilles hold, or a heelhook.
2) He straightens his leg, preventing you from doing those moves. Sink your weight down closer to his hips, and put the outer edge of his toes (his pinky toe and blade of his foot) in the side of your neck. Grip his heel and crank.
3) If he rolls, and you weren't squeezing with your knees, he just put himself in a kneebar.
4a) If he bent his leg somehow, toehold. If he straightens it, kneebar.
4b) If he figure 4'ed his legs to defend the kneebar, toehold the far foot; the one you weren't kneebarring. If he straightens that to defend it, he just let go of the figure 4. Go back to the kneebar.
4c) If he figure 4'ed his legs, figure 4 YOUR legs around that kneebar leg, while keeping your wrist in the pit of his knee. Knee pinch submission.
As long as you keep your knees pinched tight, he's bound to tap to one of those.