How long will the subscription shirts last?

As we all know, those who throw down for a yearly subscription get a mysterious exclusive shirt. 
 
Here's my problem: I have about 15 bucks on my debit card currently and don't won't be getting more for some time (perks of being a broke-ass college student)
 
My question: Are the shirts only going to be given to those who get the yearly right now, or within the next few days, or will the shirts be given to ANYONE who gets the yearly, even if it's months out?
 
Also, does anyone know what the shirt will look like?

probably the first month.