At what age did you stop wearing your LO in a SSC?

We're going OS next year, and when I mentioned taking the carrier for DS as well as the pram, he asked whether we would use it still with DS, who will be almost 2. So was just wondering at what age you stopped wearing them? And as they got bigger, how long you could comfortably wear them? My plan was to have the carrier for DS at the airport for our stopovers so DD could have the pram, and then also, if we go anywhere that an umbrella stroller isn't good, eg a decent walk or steps etc, to use the carrier. We have a catbird baby piccolo and I've just ordered the extra belt for it, which I think makes it similar to the ergo in how you wear them.

I can still comfortably carry DS in my Bb fb.

He's 4.5 and just hit 19kg lol

I carried my 4.5yo last year at Ayers Rock/the Olgas trekking. She was over 20kgs.
I think your plan's great. I just did a trip to Sydney. Mum assured me there was a pram I could use but TBH most of the places I wanted to go (using mainly public transport) it was a PITA and I wished I had just brought my carrier.