My DD had some swings. Until about 6-7mo, DD went 1x per day everyday. Then we started solids, and it went as high as 7-8x per day and as low as 1x per week. I think it was because of the types of food we introduced plus her digestive system just getting confused. By 8-10mo, the swings narrowed a bit to 2-3x per day to 2-3x per week. With each swing, we tried to compensate by giving more binding foods (banana, applesauce, bread, etc) or more loosening foods (prune, prune juice, pear, peach, etc). With teething, we see more loose consistency in poop off and on though no change in frequency. Now DD is 13 mo, and she goes pretty much 1x per day. One interesting thing is it is a little bit psychological for her so she doesn't poop when we are traveling or when we have overnight guests. We went to my sister's wedding so we were traveling for 5 days, she did not poop the whole time. When we came back, she caught up by pooping 2-3x per day for a couple of days!
For your baby, if it's been consistent, I wouldn't worry too much about it. But if the increased frequency coincides with other issues, it's good to wonder whether they may be related. He might be begninning to react to what you are eating. DD started to be allergic to my dairy consumption at about 3 mo. Is he EBF? Then I would think about your diet. Are you having diarrhea? I feel DD and I sometimes have the same digestive issues.
At least he is not constipated, that is always worse than going too much - trust me!
Good luck!