every 3 days.
When it breaks
I like to change my string once the tension becomes an issue and typically before this. Once the strings is broken in I keep an eye on it and once I notice that it doesn’t hold neutral tension well anymore or is looking a bit worn I change it. I’ve lost 2 yoyos by waiting too long before changing my string so I try to be cautious. Better to swap out a string that cost less than a dollar than to loose or damage a yoyo that costs over $100.
I change my kitty strings often… they rock tho i change them after a full day of use (about a couple of hours). I have dragon string on all my good yoyos right now though… On my MN I’ve had the same Dragon string on it since National YoYo day and its only now starting to show wear like it needs to be changed (ive also washed it so its nice and white still ). I’ve played the MN at least an hour a day since then so they last a LONG time. I’ve used YYE string and that seems to have to be changed like every hour or so to prevent breakage. So basically it depends on string and how much wear i put it through.
About every 2 days after good use of the particular yoyo.
I like to conserve strings because I don’t want to pay money, but, I would say anywhere from 2 weeks to a month. Sometimes even more, but I think I let it get to the point of being ridiculous.
Full poly usually once or twice a day.
with yye poly… a string last from a day to a week :-\
With YYE poly, how can you get it to last a day to a week? Mine will last like 3 hours before I start having tension issues
That’s not good, might damage the yo-yo.
I don’t change my string very often. I have had the same string on my yoyos since March. Mine don’t really wear out very much, and I replace them when they get dirty, which never happens, I don’t yoyo with dirty hands, or when they finally start to wear out.
Lol my dm2 is so dented you practically can’t find a regular curve. But, being awesome, it has zero vibe and still plays like a champ, anyways. I’ll change that habit when I get my Sasquatch in the ma
il, yogi edition 
I have no idea why that cut off in the middle…
I generally change my string when I have to adjust string tension every other throw…usually after every 2-3 hours of play…
Typically twice a week, if not more. But it all depends on how much you throw and what kind of tricks you do.
Weekly-ish. Whenever it gets grimy enough that it snags or doesn’t respond right.
Toxic’s dragon string. Wash once a week with my cloths. 1 month and hasn’t worn out. :-\