Moving the O2 sensor

[Bunger]

Please stop me and point me to the correct thread if this has already been covered. My mind has been focused on increasing my mileage lately (I'm normally a speed freak kinda guy), cause I'm tired of all the money I toss down the gas tank filler.

Reading through a number of articles, I noticed some complaints about the O2 sensor reacting too slowly to changes. In some vehicles, I've noticed that the O2 sensor is mounted a good deal downstream. Why not move it more upstream? Doing so will increase its response time.

Also, having a A/F guage mounted in some of my vehicle (mostly just to make sure I'm not running lean under high boost conditions), I've noticed that as the O2 sensor gets older, it also reacts more slowly. So maybe that factory recommended 30k miles isn't such a bad idea after all.

Any thoughts or comments?