Ideally every 3 hours, max 5 hours but try not to stretct too long an interval - it'll affect supply in the long run. I dedicated one compartment in my freezer for bm. But i dont really need that much because I'm pumping for baby's next day consumption.
3 hours, it depends on your supply. If you are a low supply milk you excess milk may be used up during leaps. If you are a over supply mother you may need to invest in a freezer to store the milk.
Depend on individual supply. I am a oversupply mummy initial first 3 month 3 hourly need to pump. Then 4 hour then 5 then 6 max can go 8 hours.
Ideally 3 hours but do not have very long gaps in between as the body needs to get used to the demand and will maintain milk supply accordingly
try to keep your total amount of time pumped per day at 120mins to maintain supply