I play my guitar almost every day. Do I need to keep the strings loose or is it alright to keep the guitar tuned up?
The Short Answer:
Keep your guitar tuned up to pitch, especially if you play it regularly. There’s really no reason to detune a guitar that you play regularly and, in fact, it would be pretty inconvenient if you had to completely retune it every time you wanted to pick it up and play. Guitars were designed and built with string tension in mind, so you can safely keep them tuned up to pitch, even if you’re not going to play them for a month or two.
The Long Answer:
If you have a steel-string acoustic or electric guitar, there is a metal rod inside the neck called a “truss rod.” It’s adjustable, and its job is to counteract the tension of the steel strings. It bends the neck backwards against the string pressure, and the net effect is a neck that stays relatively straight and stable.
So, you can keep your steel-string acoustic or electric guitar tuned up to pitch and not play it for months or even years without having to worry too much about damaging the neck. Some guitars even have additional metal or carbon fiber rods inside to provide extra stability. Your bigger concerns should be temperature and humidity (read my in-depth article on humidity here).
Now, Classical or nylon-string guitars are a different story. If you’re not going to play a Classical guitar for a long period of time (say, more than a few months), then loosening the strings may be a good precaution because Classical guitars usually do NOT have a truss rod inside the neck. The reason is because, under normal playing conditions, nylon strings simply don’t pull on the neck hard enough to warrant one. However, if left unplayed for many months while tuned up to full pitch, and the neck can indeed take a forward “set” (the neck becomes permanently bowed forward).
Some of the more modern Classical guitars may have carbon fiber or similar reinforcement rods in the neck. Check your model’s specs and if this is the case, you can safely leave your Classical guitar tuned to pitch at all times.
Hope that helps!