The normal oem petrol filter do not last very long. I normally change mine every 6 month as they are cheap anyway. Especially if you're used to pump petrol everywhere i.e. any station you come across. Some old petrol station have very dirty stoarge tank and can clogged up your filter very fast.
I normally feel more power after a petrol filter change. Maybe its just me. If have the budget then convert to Earls' or Aeromotive lah...