Good information here. Nearly every employer of mine (military included) required me to recertify every two years in either emergency or standard first aid. I was working in security and loss prevention. Much of what is mentioned here has been engrained into my brain. It is always good to refresh and retrain. I have first aid kits in various places in my home and in my vehicle, and I regularly check them to ensure their contents are fresh and that nothing is missing. I carry an IFAK in my range bag also.
Besides various levels of first aid training I've got a range of kits from IFAK to fairly advanced kits that I use during woods time, travel and at home.
They've come in handy when I've gotten chewed up. But I need to add a medical stapler or two, and some extra stuff.