Let's face it. After a CR gets out of school, it's tough to force oneself to practice daily, but that's necessary for gaining/maintaining your speed between gigs. When one takes too much time off from practicing, speed suffers, so one way I've been coping with this reality is by practicing
I think the key is to have speed goals for yourself just like you did in court reporting school, and sitting for additional certification tests is one way to carve your goals into stone. You have a concrete day and time to realize your speed goals, and you get results in print about where you stand (on that particular day on that particular material). Just remember that those test results are only a snapshot of roughly 15-20 minutes of your steno writing career and aren't a be-all, end-all analysis of your writing.
And don't underestimate the power of mental steno and/or whipping out your machine while watching TV or listening to the radio. (Just TV for writing on your machine, though. I do not condone writing on your steno machine while driving.) It's great practice for briefing on the fly and shortening your writing. Start thinking of ways to shorten common names and terms to one stroke. You'll thank yourself later.