No, there is no reason to turn this into a Tapjoy farm fest. You can easily gain 200+ crysrals daily which is plenty. If you are buying character packs with your crystals, you are wasting your crystals, especially if you are not purchasing more crystals. You are better off spending your crystals on energy and cantena refreshes.
I did a survey that popped up in game a few weeks ago. It was mostly about what it would take to get me to spend money on crystals. Maybe I got it as I've only spent $4.99 on the Dooku pack. One of the questions did ask if I'd be willing to watch ads to earn crystals. I did answer yes. I see no problem with it if they don't make it intrusive for those who aren't interested.
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