Fact: Improving your guitar playing doesn't require practicing for 3-5 hours every day. Here's 3 ways to get better fast with limited practice time:
Plan Out Your Practice In Advance
Deciding what to practice moments before (or during) guitar practice leads to wasted time spent trying to think of what to work on. Planning your practice time in advance allows you to determine a plan for exactly which items to practice to reach specific goals. This way all you need to do is practice what you set out for yourself.
Week 1 -
Monday - Technique
Tuesday - Songwriting
Wednesday - Technique and Improvising
Thursday - Improvising
Friday - Technique
Saturday - Songwriting
Sunday - Rhythm Guitar/Fretboard Visualization
This also reduces the amount of mindless noodling and distraction that occurs when you are struggling to think of what to practice in the moment.
Practice Things That Improve Multiple Skills At Once
Not all practice items help you improve your overall guitar playing as efficiently as others. For example, practicing switching between open chords does not improve the same skills that practicing directional picking over scales does. Making your guitar practice time as productive as possible (when you don't have much time) means spending the majority of it working on items that give you the most results at once.
Take the time to sit down and review all the different items you want to practice to find out: 1. Which ones improve the most variety of skills at once and 2. Which ones help you reach your musical goals fastest. Then plan your practice time around them.
Track Your Practice Closely
Don't simply practice and hope that you are getting better. Track your results every week to determine which items are helping you get closer to your goals and which ones are not. Tracking your progress consistently also helps you identify your strengths and weaknesses, so you don't spend too much time on things you've already mastered (a common mistake made by many guitarists which wastes tons of time and slows down progress).
Applying all 3 of these concepts into your guitar practice helps you make tons of progress regardless of if you're practicing 30 minutes per day or 3 hours.
However, there are more ways to make your guitar practice even more efficient and effective. Work together with a guitar teacher to get the best results possible from your practice.