Generally I wouldn’t touch up unless you need to- so, unless you notice a problem with the design, or ink fades or falls out, or something.

It's more when you go into realism, micro tattoos, or very delicate scripts you will be more likely to encounter the blurred lines issue. It doesn't have to be huge -and styles such as american traditional have those line gaps and weights. as that will allow the ink to settle and spread a little - without becoming muddy or running into each other. My advise would rather be to go for slightly bigger designs with more space between the lines. It won't make it look crisper and more defined for more than maybe a month or two, until it starts properly healing. So unless something fell out during healing, or have faded drastically - there will be no point in touching it up. and that didn't settle down until 6mnths later. But that also means the new ink is a whole lot fresher and less settled - so there was a very distinct difference between old and new. Artist only touched up the parts that had fell out, and I am fine with that. So my tattoo had been healed for 4 months, and i went in to freshen up the red.

I've only had one touch up, and that was due to some colour falling out when healing.

Getting a touch mark made