Dd started to climb out of hers at about 6 or 7 months. I had to change to the seat attachment as we needed a harness for safety reasons. she couldn't really lie down in it comfortably by then anyway as her feet were touching the ends! I think you have done well to get 13 months use out of it to be honest.
btw our set (M&P ultima) has a base which the pram and seat unit click on to so seat unit at same level as pram was and can still be rear facing. So I can carry one the embarrasing onesided conversations and nursey rhyme singing to my hearts content (and be so distracted by dd that I drive her into lamp posts every couple of minutes) its very cumbersome though....
My dd was 16 months when I stopped using the pram. I loved using it to do the school run and like you enjoyed her being at a higher level and could chat away. Also dd got a great view from where she sat in the pram.
I used another pushchair for town trips - my dd never slept in either pushchair or pram from around 6 months and would only have a nap in her bedroom anyhow.
I was sad when the pram went back to my neighbour, she had insisted I borrow the pram and it was lovely to use.
I got mine from ebay it actually may end up back there sometime soon as I can't get it on the bus (I need it to fold small and it really doesn't!) so it is of limited use to me now. can't bring myself to put her forward facing quite yet though so I can only go walking distance from home!
I had the same one as LVOC (and a green version for my dolls as a child!), sadly dd only lasted 8 months in it before she started hurling herself about in it, even when strapped in with reins. Although she loved being up high and I loved having her facing me, it wasn't safe.
You could buy little toddler seats that go across the pram, my mum had one, but I think the idea of them was that your toddler sat in it at one end while your second child slept beneath at the other. Don't know how weird it would look to have one over an empty pram, if you know what I mean... I've never actually seen one in use since my late 60's youth and tbh don't even know if you can buy them anymore... sorry, not helpful!
I was heartbroken when she stopped wanting to use it...
Will he not lounge back if you put the folding bit behind the mattress up? My 10 month old wouldn't just go to sleep in it lying down, but if you lean her back, she'll look at a book, and then doze off. Same when going for walks. For what it's worth, we have the M&P pushchair too, and so she still faces me.