Ros is correct. Depending on the permeability, pressure, the amount of free water and salt water and fracturing of the production Formations, some oil wells can preoduce for half a century or more. The "Indiana" and "Oil Creek " wells of the "colonel Drake" days (1859) are still producing as "stripper wells" A stripper well is a seepage hole that collects about 10 barrels a day or less. In NW Pa , there are still a bunch of plastics and paraffin using industries (several companies that produce scented candles Etc).
Mom and Pop oil field stripper wells and some pumping wells are still all over the NW PA area and some of them are pumping oil from wells that are almost 100 years old.
In other areas, like The Wst Texas or Kern County Cal oil fields we have wells that only produce for a few years to some that are over 50 years and going.
When a well stops peak production, we can go back in and mess with the rock (making lotsa cracks so that oil can flow freely) we also can outfit the wells with gas (CO2 spargers, and hot water fluid extraction seystems to do wjhat we call "secondary recovery". WE can also go in and snake wells sideways around an old field and suck up the residual crude like sucking up the last bit of a milkshake.
Ya gotta look almost at every well's production records separately