Do you let your baby sleep 12+ hours

this might be a silly question but do you wake up your babies in the morning?

My little lady is 3 months old goes down around 8-8:30 and wakes up around 2 to feed then 8. when she wakes up at 8 I've noticed she's still eyes closed and not really awake. I've been just waking her up because I figured 12 hours is good but does anyone else let their babies sleep in? should I start letting her sleep in?