Frequent loss of 02 sensors..

I purchased a 98 Mustang LX V6 a while back. Check engine light came on soon after, thought nothing of it, code P1151. Mechanic stated 02 sensor needed replaced and did so. However, this past week, the check engine light has come on again, again diagnostic code P1151. This is a light driver, 2-3 days a week out of the garage. Maybe estimated 800 miles since last 02 sensor change, if that. Idle is still what it has been since purchase, about 600-700rpm.

Obviously, the answer is not to replace an 02 sensor every 6 months. Mechanic has suggested a possible short in the wiring of 02 sensor. Can anyone else help me shed a little more light on what may or may not be going on, so I can minimize time in the shop chasing ghosts?

Oil usage is standard, exhaust is no more noticeably different than any other vehicle, though I do not quite have the eye to determine small differences that might occur. Gas mileage doesn't seem to have changed much but I will keep an eye on it over the next few days. Also will check the plugs and reply again afterwards.

Sorry about the disappearance, guys. Midterms -- they eat all your spare time.

The coolant and oil seem fine, no bubbles in the coolant. Also, a few days ago, the engine light shut itself off. I am wondering if this confirms the harness short? I'm in a heavy snow area and the light shut itself off as everything finally thawed out again, could this be related at all? Either way, I'm hoping it at least makes this a much less serious issue. Send me some good news.

Any further ideas, gents?