What is the longest that you can stand for your fingernails to be before you have to cut them?

When my nails hit my keyboard before my fingertips do

I cut them once a week when they have noticeable white boarder and slightly longer than my finger.

But I use my finger nails in my work a lot so I need to actually get surface with them.

For me it's when dirt accumulation becomes noticeable and I feel like hiding my nails around my co-workers. The length is way less of a problem than the visible dirt.