I tend to play generationally, on normal life span so I don't stick with the same sim for too long. But I do get attached to my sims. What I find though is that when I create a baby for my favourite sim, I really like the baby and toddler because it's part of my favourite sim. And once it becomes a child and teenager I have already started to become attached to it as its own sim person because I'm investing time into building its memories and life events, and I care about what happens to it. So, by the time it becomes a YA I've become more focussed on that sim than it's parents, and it's parents (who were originally my favourite) start to become periphery characters, and the cycle begins again with the next generation.
I play all of the sims, but my focus and attention gradually just naturally shifts onto the new sim. I'm not sure if that's what will happen for you too. But I find that when the sim is a child, if I think of it as starting the journey to creating my YA, it feels quite easy to play - I'm not sure if that's what you mean? I think you should just give it a go and see what happens - maybe you'll find a new way of playing you like even more? :)
