I am 6'4" and have ridden 180 cranks for more than 20 years. If lengths longer than that were commonly available and did not add complexity to custom frame manufacture, clearance, etc, I think I might have gone longer. That said 20 years ago I rode all of the surrounding terrain using an 11-23 cassette, my cadence was low and I 'felt' efficient grinding out the hills (Boulder, Colorado, so reasonable climbs). With age and multiple knee surgeries on both legs I have slowly increased cadence and changed gearing. I now ride a 12-27 and sometimes wish I had a 28. I don't think I have slowed down noticeably, just don't enjoy the pain that I used to and I believe longer cranks, with higher gears are more destructive on ones body irrespective of inseam. I hate to think how little cartilage I would have left were I actually riding 195 cranks!