This sort of product will fail to achieve any short term or long term benefits over regular training. In fact, some results show that it can hinder performance.
People believe these sorts of products can increase their red blood cell count by reducing oxygen levels, similar to the way training at altitude can increase red blood cell count.
The problem is that the body doesn't work that way. Red blood cell count only increases after about 3 days of continuous training in an oxygen deprived environment. When you're using these face masks, you're putting them on for an hour or two a day, and then going back to breathing normal air. Doing that will prevent the body from increasing red blood cell count. It has to be on continuously through the week, which is very impractical if not impossible.
Studies have been done on these devices. The people who wore them for an hour or two per workout, 3 times a week, saw no benefits whatsoever and no increase in red blood cell count compared with a control group doing the same workouts.
The following web site does a pretty good job of debunking it:
Hope that helps!