The student upgrade key works like a Retail key. So you will probably need to
Activate Windows 7 by Phone on subsequent installs, particularly if there is significant hardware change such as change of mobo or hard drive. You should know that only one system can be activated at any time with a single key. If more than one system using the same key is online at the same time, the key may be black-listed.
A better option is to image your system using either the inbuilt windows backup utility or apps like Macrium Reflect or Acronis. There is a Macrium reflect tutorial on this forum. Check in the tutorials section. Image your system when you have tuned it the way you like with all your apps installed. Then, when you want to, you can just restore from the image, no reactivation required.
I purchased the student pro version from Digitalriver. They made me run circles for the disk. Ultimately, the matter had to be escalated to MS and they sent me the disk, a full 2 months after ordering! So be careful, where you buy from.