The problem with keeping both the keys to your filing cabinet on the same keyring: when you lose the keys, you lose both keys to the filing cabinet.
The advantage to keeping both keys to your filing cabinet on the same keyring: when you find the keys, you find both keys to the filing cabinet.
The thing that really makes me happy: that I remembered where I'd put the keys to the filing cabinet just before I googled, "How to break the lock on a filing cabinet."
The keys to the filing cabinet now reside in two separate places. One of which is the keyring containing my house keys, so if I lose the keys to the filing cabinet, I automatically have worse problems to deal with.
I'm having lots of fun organizing my home office as I unpack. I'm getting to decide where to put things based on where it makes sense for them to go, rather than where they seem to fit at the time, and I have fantasies that this is going to suddenly transform me into a neat and organized person. I expect reality will kick in by the end of February. Still, I'm getting to make some real usability improvements in my home office, and this pleases me.