I think that's my sweet spot, 30/3600 or 120 steps per minute. At that rate I'll have no problem doing 10K steps in 90 minutes and that's my real goal. Some aching in my knees today. I think 60 minutes (ok and 55) is overdoing it a bit. I'll keep 50 as my max for a couple of weeks and try 60 on the weekends again next month.