Yes, many people take their guitars to a store to have their strings changed. Let’s DIY, shall we?
How do you know when to change strings? Or do you just change them once a month or so?
You change them when you want
It all depends on you, your needs, your desires, how often you play, your skin chemistry, the type of strings you use, how clean your hands are when you play and probably a bunch of other factors.
With that said… I have in the past changed strings as often as weekly. I currently have my guitar in my office with strings that have been on for months. My plug in guitar that gets played out gets changed about every 3 or 4 performances. One reason for that is they are different strings. My office guitar has monels and they just last forever. As strings get used, their sound changes. That is probably the main reason people think “I need to change my strings.” Another thing that happens in extreme cases is they lose the ability to intonate well (it does not sound in tune when fretted). I think that has to do with work-hardening of the strings (but I don’t know that). As I said at the start… change them when you want
I change based on sound. But now that I’m a dealer of fine guitar strings here on the site, I recommend my students make it a weekly habit
Interesting technique; I’ve never done the initial loop, but I found it easier than any other way I’ve done it. Also, I always changed one string at a time but it saves time…
What are your thoughts when the guitar has a movable bridge? I lightly taped it in place and removed 3 strings at a time.
Most mandolins (and violins) have movable bridges. Unlike fixed bridges, on those, I generally change a string at a time. It is tough for me to be convinced I get the intonation right after removing it
If I have fret maintenance to do, or if I want/need to do serious cleaning, I’ll bite the bullet and remove them all.
Lightly taping seems like it would work fine (although I haven’t done it).
I recommend just doing a couple at a time. I do a pair at a time on mandolin, and one at a time on banjo.