Does my dog need anal glands expressed?

So when my dogs have pudding like poop, they scoot afterwards. I took that as a way for them to wipe their bottoms. I keep reading that when they scoot, that means that they need their anal glands expressed. My dogs do not scoot regularly. Maybe once a week if that.....again AFTER a pudding like poop when they have a different treat or something. If their poop is firm, they do not scoot. Need I be concerned?