There are 2 types of usable time; Bonus Usable Time as part of your Management Plan and Assistance time purchased separately.
Any unused Bonus Usable Time is forfeited and the end of the month. This includes Bonus Time as part annual and monthly maintenance plans.
Assistance Time is purchased separately and lasts for 12 months. You may purchase Assistance Time in increments of 0.5 Hours with discounts for bulk time purchased.