Book Buff Duration

While the Fields/Grounds of Valor system is quite awesome, I have an issue with the Field Support system. The buffs that you can get from the books all have different durations, making it hard to remain fighting optimally for extended periods of time. I understand the need to keep tabs costs cheaper for lower level players, but I would personally love to see an option for longer durations on Field Support.

The following is a partial list of how the new menu could read:

White Magic: Protect (30 mins) 15 tabs
White Magic: Protect (60 mins) 30 tabs
White Magic: Shell (30 mins) 15 tabs
White Magic: Shell (60 mins) 30 tabs
White Magic: Haste (15 mins) 20 tabs
White Magic: Haste (30 mins) 40 tabs
White Magic: Haste (60 mins) 80 tabs

This way you are maintaining the current duration/tab cost for those that wish to be frugal while giving others the option of spending more tabs for the added benefit of not having to run back to the book every 15 minutes. I think this could be pretty easy to implement without causing any major imbalances.