There's 18 months between my two. I have a P&T but I also sling DD, while DS goes in the (single) pushchair, so I don't just rely on the P&T.
I have, frankly, thighs that can crack walnuts thanks to sling-ing DD so much. There is no way I'd be able to carry DS, too. I mean, I'm sure I could, but why the feck would I, when it would be so cumbersome and heavy, and it's easier just to pop him in the might McLaren?!
Fibilou - good for those people you know, but surely you can see that double slinging isn't for everyone, because everyone has different circumstance.
Everyone has different requirements, needs and priorities when it comes to moving their DC from A to B, which is why there is such a wide range of products on the market.
I can never understand why people find this concept so difficult to grasp.
. Why do people think that because, say, X works for them, so it should work for everyone?
Seriously. Just get on with what works for you, and trust that everyone else has the same nous to make the right decisions and purchase for them.