Absolutely - identifying goals and focussing are vital to effective use of practice time. 30 minutes committed practice Vs 2 hours noodling - there's no comparison.

The only cautionary note I'd add is that you must also find time to enjoy it. I took the last of my exams a while back, and was practicing with maximum focus for months at 8 hours a day in addition to playing gigs / teaching etc...

I got so sick of it that I now have barely played for 3 months. I know I will again, and the improvement I made over the year even after playing for 22 years was huge... BUT it's easy to lose sight of why we all do this in the first place...