For what it's worth, there is IMO, a serious risk of "over-filing". You need to work out a system that works for you, based on what you need to do with the paperwork. Some things are kept because we need to refer to them again often. Other things are kept in case we might need them again. They require different levels of attention I think.
For example, it may not be necessary to split up your utility bills and file them under "gas", "water", "electricity" etc. It may work well enough for you to just file all together. It does for me. When I need one of them (very very rarely), then I check through the section and then find the one I want. Yes, it takes me more time than if I'd separated them out into different sections, BUT this is offset against the time I saved in just filing them together in the first place. You need to work out what you're keeping stuff for, how you will use it and then it becomes easier to see how to file it.
For backlogs, I would do a rough sort first into "keep" and "chuck". Then if I had time I might sort the "keep" pile into "old" and "recent". The "old" stuff would get filed together as one pile and the "recent" would get filed under my new system. If you find out later you need something from your "old" pile, well at least you know where to find it and when you need it, you'll be motivated to look for it.
Since our filing is kept in the office, on the second floor of our house I have a magazine file in the living room for current paperwork. When mail arrives I open it straight away, bin the stuff I don't need (including random little leaflets, envelopes etc that come with the important stuff) and put the rest in the magazine file. Once every 3-4 weeks I sort through the magazine file, pay bills, chuck anything now out-of-date (info from school etc) and file what's left.
The actual filing upstairs is split into broad categories - house, bank stuff (loads of different acounts all thrown in together), bills, insurance, medical stuff, other and stored on a shelf in magazine files. I just bung the pieces of paper the file (no time spent punching holes, putting stuff in plastic wallets etc).
Every year I archive things - take "old" things out of the magazine files, put into carrier bag, label with the year, put into cardboard box.
The key is to find a system that is easy for you and takes only the time that you have available to spend on it. A beautifully filed set of paperwork may make you feel satisfied when you create it, but if you don't have time to manage it properly you will end up feeling even more frustrated. Do something that is "good enough".