How often do you sharpen your knifes?

How often ?
When they need it.
If I don't have time to sit down and use a Arkansas stone. I will touch it up with a steel. Lately I have been cutting out some thistles and will get in the dirt.
So time to touch it up.

 

OP, you're probably gonna hate this answer because it's gonna be super vague, but it's true for me.

I sharpen a knife when it needs it, which means when I notice a significant decrease in performance. I prefer toothy "working" edges, so it's a fairly quick process for me, couple licks on the bottom of a coffee cup or a diamond hone (or a mill bastard file and/or coarse carborundum stone for a machete). I never reprofile a knife that I've already sharpened to my liking because I have to reprofile almost every knife I own to get it to "my" angle, the one I settled on after several years of sharpening and knife use, which I no longer have to think about. Once a knife has "my" edge profile on it, the only thing the sharpening really does is refresh that angle, so there's no need to reprofile until and unless the blade gets worn enough that the edge is significantly thicker than when it started, which takes a long time and a LOT of sharpening. I would say I sharpen my carry knives about once a week on average, less with the harder steels or less used knives, more with things like my Izula that I beat the snot out of on a regular basis. If I'm using a machete heavily, I carry a file in my bag and hit the machete with it fairly often (multiple times a day), because I'm in a temperate woodland area with a lot of rocks in the ground from our limestone bedrock. Very easy to roll a Tramontina edge on a rock when you accidentally overswing and hit the ground.