Maybe not all the way back to square one.....but back up a few paces and see how they sound.
Personally, once I can play them (this goes for any rudiment or pattern) then I try to practice them through a variety of tempo ranges and subdivisions. That way, when I want to employ them on the kit, (hopefully) there is little thought put into it....I want 'em to just flow.....whatever the tempo.
+1 on the different subdivisions! You might be able to rip paradiddles at a good clip, but can you think in triplets while this is happening? To quote Jojo Mayer: how fast can you hear? When practicing different subdivisions, keep time with something (your right or left foot, a metronome, song on the radio, etc.), and practicing shifting from one subdivision to another without stopping (eighth notes to triplets, for example).
Also, move the accent through the paradiddles, to gain even further control over your stick movements. By this we mean play the paradiddle with the accent of the first note for one measure, then with the accent on the second note of each paradiddle, then the third, then the fourth, at a slow tempo without stopping. Pay attention to upstrokes, downstrokes, taps, and full strokes as they occur.
It's cool that you can play paradiddles, but can you also play through all of the paradiddle family of rudiments (single, double, and triple paradiddles, and paradiddle-diddles) in various combinations? Practice switching from one paradiddle rudiment to the next without stopping. Note where the accents fall in relation to the quarter note pulse; can you make up a musical exercise by combining paradiddle rudiments?
I agree that slowing down for its own sake is a necessary first step, but after that, you should slow down so that you can focus on different aspects of your technique, or add challenges to things you can already play at a decent speed. Also, you can see how your technique must change subtly when playing the same thing at different speeds.