I'm aiming as low as I can without having frequent hypo's. How low this means I am varies, but I find all numbers acceptable as long as I try my best.
And sometimes I choose to eat or do things I know will mess up my TIR, but if that's a conscious choice it's worth it sometimes for me. On those days I'm not bothered by more highs or lows than usual.
Same goes for days I'm ill, or when I have something else going on which is more important than staying in perfect range all day.
If I'm helping someone move house, driving and walking stairs with heavy stuff all day, I aim for higher numbers than when I have a lazy day on the couch with all the time to pay attention to diabetes.
As for the range I've set on ly Libre, I regularly change it, depending on how well my diabetes is behaving. I like to show it as being in range about 80% of the time.
This allows me to easily see where I can improve without showing as either in range almost all of the time or out of range almost all of the time. Seeing I'm out of range all day doesn't improve my mood, and doesn't help improving my diabetes, it's useless. Same goes for seeing that I'm in range all day.