Actually, per the witch rules, I only need 6 hours. 1 hour per spell level of each scroll...so 6 first level scrolls. I think they balance the shorter time with the fact that the scroll is destroyed if the spellcraft check isn't made.
Go for it. Not really a balancing factor imo, not that it really needs to be, as most Witches can likely take 10 and auto succeed. They do have a far more limited spell list than Wizards afterall.
