When learning how to play a guitar, a defined form of practice is always better and preferable to unstructured routine at all. A structured routine always enables a person to easily achieve their goals. Following are the benefits of having a planned short period of guitar planning rather than having none at all.
A planned guitar practice will give you a sense of responsibility for your action. For instance, you could have planned to learn in a month. After two weeks of practice, the sense of time will enlighten you on your progress and define whether you should play more or lower your pace. When you do not have any goals set at all, anything goes by. You do not have a clear way of how things should get done and you therefore end up achieving so little that is if at all you will achieve anything.
When you have a focused form of practice you can easily identify the kind of music you want to play. When you are purpose driven, you get the passion to play continuously. At this point you get to decide whether you want to play for your own pleasure, want to form a band, want to become a guitar god or even join a band. Unlike the short focused practice, lack of a practice routine makes you take the practice sessions for granted. You find yourself training intermittently such that you think you know something but you actually know nothing.
Often, when you set to learn and practice your guitar lessons in a short defined time, you achieve your goals faster. When you have a scheduled short plan, it makes you know of what is expected of you after the defined period. When you lack a practice routine at all, you take longer to achieve goals than you should have. This is because you have not instilled the discipline of punctuality and goal setting to yourself. As such, you find that something that you could have taken say a month, takes much longer due to lack of planning.
Naturally, human mind is designed such that it is more effective when it comes to absorption and retention of repetitive short term information as opposed to having one long piece of information dispensed once in a while. This makes short structured practice be more effective as compared to no practice regimen at all.
As the saying goes, practice makes perfect. A continuous short form of practice will help improve your guitar playing techniques. It is always better to have a form of a practice plan since it makes you a serious, driven person.