Whatever you choose, it's up to 3 free days. Hoppers are one flat fee ($50) regardless of the number of days, so no discount there. But if you were to choose no expiration, where the cost is dependent on how many days you choose, a 7 day ticket would only cost you what a 4 day ticket would cost.
FYI--It's only about $10 difference from a 4 day to a 7 day ticket. Don't overbuy from what you need (unless you want to take the full ticket and upgrade to an AP--the no expiration option will give you a great deal as long as you use it at least once first).