(i changed my display name)
how long is "a while"? i think some amount of stagnation is normal at each level.
before i say anything else, you should know that i have my own method of training that might differ from what you've seen others discuss here. i don't like either of the popular formulas (20+N^2 or 20+N) because they get a bit absurd at higher levels in my opinion, so i use my own method of determining set length. by "set", i mean a group of trials. for example, i currently train D10B with 30 trials per set. currently, my goal with any N level is to get 80% on a set of length 4N trials.
i think you might want to try experimenting with the configuration of your sets.
so how long are your sets? you can try decreasing the set length, and increasing it once you master the previous length. for example, i achieved 90% on D9B with 36 trials, and that's when I moved up to D10B. when i first started with D10B, i only used 20 trials per set. i got 100% on that, so now i'm using 30 trials per set. once i get at least 90%, i'll move to 40 trials per set. i did the same thing when i reached P5B. i hit 80% on P4B with 16 trials, so i moved up.
lastly, i don't imagine that the same thing will help two different people break through plateaus. at the end of the day, i think your best bet is to experiment and make changes to your training routine, and find out what works for you. for example:
- if you train in the morning, try doing it at night (and vice versa)
- try increasing/decreasing your session length
- revisit the level below, then come back to D5B once you hit 80% on D4B again
- try taking a break from training altogether
hope that makes sense?