I leave it too long... like far too long, habitually.
My hair looks best at this sort of length:
I get it cut far too short so I look like this for a couple of weeks:
Then it looks good for about three weeks... then it gets too long and I say "wow I need a haircut"... and then I get a haircut like 2-3 months later when I look like this:
The last one is an exaggeration but it gets long. My hair grows really fast
.
In an ideal world I wouldn't get it cut as short, and I'd get it trimmed like every 3 weeks. But who has the time??