Yes, they certainly can. Apple allows any apps notifications to be switched off at the OS level - it isn't optional. My users love the notifications though, and

Yes, they certainly can. Apple allows any apps notifications to be switched off at the OS level - it isn't optional. My users love the notifications though, and they commonly customise to get _more_ notifications. The reason it is 4 months is because iOS only allows 64 notifications to be scheduled in advance for any app, and if they want users can configure to schedule that many in a 4 month period.