Somewhere around age 40 I fitted my heavy, MTB-based commuter with much longer cranks They worked and still work well with my custom high gearing. I have always been a masher rather than a spinner. However, I turn 57 next month and have found my knees don't like mashing anymore, and the longer pedal travel can sometimes aggravate my hips. I have lowered the gearing on my other two bikes over the last year, but my MTB commuter already has a very low gearing range. I have serious thought of of refitting shorter cranks.

I don't remember exactly, but I think I went from 168 to 175mm cranks.

Even with the slight knee and hip aggravation I love having longer cranks....for now.