I just solved this at my house (I hope!)!!
I FINALLY realized that I would NEVER be able to keep a filing system. I'm too much of perfectionist (and then procrastinator) and if there's a peice of paper I don't have a file for, then I would have to create one, but it would have to have the perfect label and the folder would have to have the right tab so that it fit with the ones before and after it. There just aren't enough middle tabs for that!
So, I purchased some document boxes (got mine from the Container Store) and I will pile in those like I pile around the house. I don't mind searching through a pile of papers - if I know the paper I need is in it. But when I pile around the house without any organization/categorization, I can never find what I need.
So, right now, I have a house box, a financials/impt. papers box, a pet box, a health/insurance box, a warranty box (though, I may try to find another way to organize these so the warranty info/instruction booklet is in the same room as the appliance), and I have a temporary box for mail and stuff that gets piled on counters. When that box gets full, it gets gone through, stuff thrown away or moved to their appropriate boxes!
I'm super excited about my new "filing" system - can you tell???!!!
As for the rest of your question - there's all sorts of info online about how long to keep certain types of papers. In my box system, it doesn't really matter until the box gets full. Then I can look and maybe have an "archive" box if necessary. Boxes are easy to change categories and add when needed.