Both my bubs hit the 10kg mark around 10 mth and I found baby wearing in a one shoulder sling after that point hard. We got a rigid backpack with DS which was good but cumbersome. We have an Ergo with DD and I love it as it is easy to transport (scrunches up into a bag) and we can do a front carry when she's sleeping, hip carry or back carry.

She is currently 13kg and I don't even notice her weight and can easily carry her for 3-4hrs