Yes, you need to be reachable and you need to have somebody reliable checking your mail. When they call you for the exam, you may only have 10-14 days notice and although you can re-schedule the test date if it's not convenient for you, it's a big hassle if you do that. They will not let you pick dates to schedule to, instead, they will contact you again at some unknown point in the future and give you a similar 10-14 day notice to appear. Same with the oath. Somehow Canada seems to think that citizenship should be important enough to you that you will bend your schedule to fit their needs and not the other way around