There is some confusion here, methinks. Some are talking about the drain plug gasket (90430-12031) not the gasket on the filter itself. I also have never seen a filter that came without its own gasket.
The drain plug gasket is different. Manual recommends it be changed every time and that is best practice. I have never had a problem using one twice and I never do more than twice. Mostly I change them every time if I have one available. I have taken off ones of an unknown age installed by PO's or other mechanics that were in pieces or leaking due to excessive compression from multiple torque-downs.
As far as cyclops13, ask your mechanic what he does before the next change. I'm sure a lot of them change out with generic washers. There aren't that many sizes. I'm also sure there are plenty that will reuse beyond what is ideal.
Amazon sells a 10-pack.
Amazon.com: Genuine Toyota - Oil Drain Plug Gaskets (QTY10) - 90430-12031: Automotive