I don't own an ipad/tablet so C of C's is the first game of this type I have played. By time based I mean to progress in the game you either wait hours/days to upgrade some part of the game or you buy gems to speed this up(or get rid of the time restraints completely). So is this a common way to do this on tablet games or is this a new model for making money. I am sure loads of mmo or other games use this model but then I don't know as I don't play tablet games and I doubt PC games have really adopted this way of selling their games.

Yes, very common, and it actually started from web browser games.

I don't know exactly who's first, but Travian is one of the early games to do this. Before cellphones were smartphones, before tablets existed the way they exist today, before Facebook got popular, web browser was the perfect platform to build this kind of games. You can access it from anywhere, from home, from work, from library, and play. Unlike the traditional PC games in which you have to install to a particular machine and play it only from there, logging into a web browser can be done from anywhere. So you can pick up your progress, that you started from home last night, at the office the following morning.

Then come Facebook, then Facebook games, then Farmville appears, then iPhone got popular, and we get to where we are today.

For mobile games yes, its extremely abused to milk money from users. Almost every mobile game that doesn't have an initial cost to install. I rather hate this model. It's like having a subscription to a game and causes most games to be "You better be rich and spend 500$ to win, or be a loser that only gets to enjoy 25% of the game and never gets to progress". I rather liked the old days of games when these types of games were called "demos" and the pay option was to buy the full game.