I have a little secret to keep it fresh...
I love the HD800's, and as such, I've built a pretty splashy rig around them, tube amp, tube dac, etc. My wife has a job that requires her to travel about a week and month and I only use my HD800 rig when she is gone. They are a novelty every time I turn them on because I don't get to use them all the time, and it is my consolation prize for missing my wife
Some people may think it's weird having a setup that is only used one week a month... I get that... But the time I do spend with it is wonderful. It gives me something to look forward too when my wife is gone and I spend hours every night, late in to the night, enjoying track after track. Every time I fire it up, I get a bit giddy - who else can say that about a system they've had for a while?
I guess what I am saying is that I agree with marcoarment and Jude; that it is easy to always want 'the next best thing' and this is my way of keeping what I have fresh and new to me.
I'm kind of doing the same with my STAX rig, with a difference: this is my only system, but I only turn it on when I feel I REALLY want to listen to music and not just spend a couple of hours with the headphones on my ears, browsing and playing and reading with my iPad. I used to spend much more time with my headphones but it wasn't time spent listening, not paying the due attention to the music.
Now I only use my 009 a couple of times a week but I enjoy it a lot.