Ford Aspire Check Engine Light - P0130

Hi

I have a Ford Aspire 96 2 door hatchback.  Just bought it around 1/2 year ago and the "check engine light" came up  in March.  Brought it to a mechanic and they scanned and found the code to be P0130.  They recommended changing of oxygen sensor which I did.  In April, the same problem recurred.  I checked with the previous owner and he mentioned that it is a recurring problem and he has changed the oxygen sensor 3 times during the single year he owned it.  Brought the car back to the same mechanic for a more detailed check, and this time they found the exhaustive pipe between manifold & catalyic conv. to be defective (leaking). I brought the car to a muffler shop to repair the leak.  Seems okie for 1 month but now the light is on again, same code P0130.

I am really a newbie, new driver with little mechanic knowledge, first time owner car.  I am getting real frustrated with the problem and also a bit concerned ..

i) Any recommendation on what could be the real problem?

ii) Is it okie if I just ignore the problem?  I have my friend resets the code and it seems to come on after 2 weeks (seems to come on every time I top up gas)

Forgot to add, the engine and car runs well.

Cheers

An anguish & helpless owner

Did you replace both oxygen sensors? There are two on the vehicle, an upstream by the manifold as well as downstream by the catalytic converter.