My tg flight is scheduled to leave LHR at 21:25. LapInfant is always asleep by midnight. I'm anticipating a lot of squirming before she settles down (she wriggles and stretches a lot going from one side of me to the other) but this is all done silently, I just assume it's going to be very embarrassing for me but I'll deal with it. Once she's done with the fidgeting that's it, but goodness help me if I try to put her somewhere where she can't reach my chest.
But this, for me, is one of the very numerous upsides to cosleeping with an only child. Since I am her bed she's happy to sleep anywhere so I'm actively looking forward to these trips.
I'm more concerned with getting some sweat absorbing gauzes and muslins then an extra seat just in case the cabin is kept too warm.
I'll be happy to admit I was wrong, but I've never once known my daughter to fuss or cry without good reason. And one of the few things she detests is being strapped to a chair.

Every family is different, in our case, and I really have no doubt about this at all, 2 Y seats would never work. But I'd never suggest another parent adopts my approach - perhaps you'd need to be a committed breastfeeder and happy cosleeper to understand why I'm not concerned about these flights.