hi,
for me my picking abillity had not changed for more than a year, just within 0 - 5 bpm. now i can paly the same shit about 20 bpm faster, within 2 weeks!!! it´s just like petrucci says on his dvd: sometimes you´ll hit the wall and you have to be really patience because one day, out of the blue, you´ll have it!!!!
another thing is playing licks from very different styles or unknown/ new fingerings, etc. will help you to improve- maybe just concentrate on working on your feeling, improvise a lot after some practice, as a reward so to speak. if you build up a mental problem- it´s the worst thing you can do!!!
another thing that helped me, personally, was, when i first added the classical guitar to my schedule. etudes helped to work on my left hand, which was effective as hell for my solo playing!!!! also it was a good reward to play the tunes, because it´s more fun, than playing scales and working on shops!!!!!
or, what is said about paganinni: he would play most of the time on a cheap and hard to play instrument, then when coming back to his good violine, he was even more impressing
i do this, too. for example: i play legato on my 7-string during the week, then at the weekend i take out my esp kh-2
it´so easy to play all the stuff that i was struggeling with over the week!!!!
hope it helps!!!
keep in mind, that muscels have to develope- it´s taking ages sometimes and the better you are, the harder it´s to push it even further!!!!( something i learned doing rpg´s, hehe)