How long should I keep my razor blades to avoid necrotizing fasciitis?

I have a Venus razor and the blades hardly ever get dull because my hairs are thin. The blades I have on are probably several months to a year old, but there's no rust on them and they work just fine. But last night I saw this show called "1000 Ways to Die", and this woman cut herself with an old razor blade where a flesh eating virus was growing and it killed her. So how often should I change my blades, or how can I keep them sterile because they're kind of expensive.|||Trust me, you're not going to get a flesh eating virus. Even so, if you want to sterilize them, and you should, just keep them in a cup of rubbing alcohol with a sealed lid. Then, whenever your need them, just rinse them with water and use. Just make sure to clean them and put them back in.