Hiya. There's conflicting information about doing abs/core every day. Traditional thinking is that you don't do ANY muscle or muscle group every day, but rather you should give yourself at least 48 hours to recover. Abs are slightly different, though, because it's very rare that you truly work them to fatigue (and you almost never lift heavy weights with your ab muscles the way you do with, say, squats or bench presses). Some instructors/trainers/national presenters say it's perfectly OK to do abs/core every day.
I usually do core workouts 3-4 times per week. After a particularly tough workout, I definitely need the day off to recover. Plus doing 3-4 workouts per week gives me lots of opportunity to do something totally different every time I work my core. I won't repeat the same ab workout for at least 10-14 days.
That being said, I *do* try to incorporate core work into almost every lifting session and most of the classes I teach. I'll use a stability ball instead of a weight bench for chest/back/shoulders/biceps/triceps. I'll stand/kneel on a BOSU balance trainer or two balance pods for standing weight work, both upper body and lower body. I'll have my classes do lots of planks in between pushups, or I'll make the pushups super slow so they have to use their core to stay in position, etc. Or we'll walk the plank sideways, do 4 pushups, walk the plank back to where we started, do 4 more pushups, etc.
Hope that helps.