I'm sure this has been covered but after 2 general searches without much success I'll ask. The injector is my razor of choice so far. Since an old blade is not pushed out until you load a new blade will it cause problems leaving an old blade in for awhile. I want to use another I have and I'd love to use it 2 weeks or a month before swapping injectors again. I have a fake blade insert but I'm not familiar with how to insert that and push the old blade out. Any ideas or knowledgeable comments?