I have 3 meals and 3 snacks every day. It helps to keep blood sugar level when you eat every few hours. If you want small, frequent meals, that is fine too but be careful - meals can add up to too many points real quick.
You should eat when you are no longer satisfied on Core. When I was doing well, it naturally seemed to end up being 3 meals and one snack in the afternoon between lunch and dinner. I always ate substantial breakfast and an early lunch so there was no need for a snack there. Sometimes, I'd have a second snack after dinner.....aka dessert.
If I was no longer satisfied and the snack was Core or if I had the points, I'd eat.
JMHO. The beauty of Core is that you eat less food because you are only eating to satisfied. That means that you might get hungry more often than others because you are not eating big meals at every sitting. I'm trying to get back in the groove. My recommendation is to eat when you are hungry and not when it is meal time. I'm personally trying to shake my sense of entitlement just because it is a traditional meal time. It will even out because somedays you'll be starving and will eat more.
I have 3 meals and 2 snacks. I don't eat breakfast until I'm at work around 8:30. By 11:30 or so I'm ready for lunch. Then a snack around 4 to hold me till dinner. I do need to plan something for night time as that is my downfall if I don't. With Core, keep snacks on hand - veggies and dip, roasted chickpeas, fruit - fresh and frozen. Eat them when you need.