But then if you get, say, 20 dragon shouts, it would be incredibly easy to spam. Seriously, they're way too powerful. You saw in the trailer, he used it only as a last resort.
Um... no? It was the very first offensive thing he did. You're gonna be fighting a lot of dragons; it's what you're meant for. You think because a dragon struck you once and then breathed fire at you, you're in a last resort situation? He used it because it's a useful tool. We don't even know what that one did. The cool down for any specific shout shouldn't be more than 5 - 10 minutes. For some it should even be as low as 10 - 30 seconds. If it's once per day, then you'll have people who enjoy the dragon shouts pissed off that they can't reuse them, and they'll be resting for 24 hours after every single combat. That's just annoying, immersion-breaking and will disrupt the flow of the game. Greater Powers had their purpose, and once a day kind of made sense. Dragon Shouts, however, should be able to be used many times a day. Yes, all of them.
maybe the closer you are to a dragon, the faster you're shouts recharge. This way you can fight a dragon and rely heavily on the shouts, while at the same time you ensure that you don't abuse it's power outside of dragon battles. Maybe it takes a while day for it to recharge when you are 10 miles from a dragon, but when the dragon is right on top of you- it only takes 30 seconds or so to recharge.
No...