What do I mean with that ? For example if you are working on running scales up and down, you should focus on it for about 30 mins for example and then move on to something else you need to improve on. For example hybrid picking.
What I found, was that when I started practicing for more than an entire hour on one thing I got a bit frustrated. When you want to practice only one single thing, it would be good to take a break in between. In my experience a break can do wonderful things.
For example I couldn't get a lick perfectly down, but after a two hour break ( not saying that you should take a two hour break, do whatever feels comfortable for you ), I picked up my guitar and I suddenly played it perfect!
So in short: I would recommend making some kind of personal schedule of things you want to practice and decide for yourself how much time you want to put in each of these things. It's possible that you don't have to take breaks and practice for more than 1 hour, if that works for you. But I would surely recommend if you start getting frustrated with practice, either take a break or start practicing something else you need to improve on.
JJ
