So, you want support them with your preorder - doesn't make sense because you take a preorder discount of at least 3 Euro (if you didn't own TF before). If you really want support them you should pay the full price at release day one
The other 15% (if you were a TF owner before)) also get the regular customer when purchasing the game at release day one or later. And regarding the discount - after the discount is before the next discount. Discounts come and go, never it will be the first and never will be the last.
And to all preorders fans here:
Do you go to your Supermarket and buy your potatoes as preorder ? Wouldn't make sense, although you can be quite sure that the quality of the potatoes will be the same as always.
Now compare this with a game - nothing is sure and the last is the quality. However, almost 100% sure is that the game has big bugs at release day one, this is what shows the experience from the past with all kind of games. And this leads only to waisted time and frustration.
So what the hell makes people to preorder an unfinished, full of bugs, product ? There is no reasonable argument to preorder, and it's the most stupid decision of a customer to give his money out of hands before getting the real product. You never would preorder any other product, but precisely with one of the most uncertain products ( in the sense of quality and usabilty) on the market you do it ? Who can understand this ?
You even don't get the game earlier as a normal (as not to say intelligent) customer who buys at release day one. You make someone already earning your money without he delivered anything.
With this stupid atitude of the immature customers game companies only feels empowered to release an unfinished product. The computer game industry laughing up their sleeves about sheeplike customers.
Others call them brainwashed customers.
My recommendation for all computer games: Wait at least a few days (better probably a few months), check the forums, read the critics, check the delivery of patches, and buy then. This gives you in any way a more pleasant game experience than at day one. Until then - I am very sure you still have a lot of games on your harddisk you can play meanwhile.