Ok I have been coming along well with my safety razor progress I am now on to whole head shave with it and trying out different blades, My question is probably a simple one but I figured I would ask. Looking at the blades some of them are numbered 1,2,3,4 with 1,2 on one side and 3,4 on the other does that mean that I can use side 1 for a couple shaves and then flip the blade and use side 2 for the same amount of shaves or should I just use it on just 1 side and then throw it in the trash?