Again, if you have a 98, its a pretty safe bet that you dont have a distributor.
Just because the manual doesnt say to replace it, doesnt mean it shouldn't be replaced. Just like any other mechanical part, the cap and rotor of a distuributor will wear over time and increase the resistance of the ignition system, which leads to late and weak spark, which leads to incomplete burning, which means less power from the combustion, and less mileage per gallon because of it. its a vicious chain
And actually, as Mensajero said, the RAV's (early-97') that had distributors DID have a service interval in the manual for it, as this is a wearing part that WILL need to be replaced sometime in its life, no matter what.