I understand that as difficulty goes up, mining becomes less cost effective. 

I'm more interested in getting as many shares as I can at a price lower than retail.  I don't care about making an immediate profit on them by selling out.  (I consider it a medium-long term holding.)

Therefore, mining is a useful way to get in at < retail.  I'm just trying to figure out how much longer we'll have at the game before it dries up.  I haven't found anywhere the number of blocks that PTS will have.

I guess it doesn't matter and I should just push hard now, without considering the longer-term mining potential?  *shrugs*  I'm sure I'll have some clock time dedicated to mining it for as long as it lasts....