Previous service plan balance hours

Ability to connect with and bring over the balance service plan hours from a previous one which might have expired. These hours will not be charged but will show as balance from previous maybe with a list of service plan hours and service plan number.

Also, what if its a 3 year plan, with annual 40 hours(e.g.), then how can we manage this, so that its cumulative 120 hours, but the limit for each year would show as 40, then next year would be 40 + balance from previous year.