If the washer surfaces are pretty smooth, they should be OK. Run your fingernail across them; they shouldn't catch on any edges. The washers are intended to deform when the correct torque is applied to the injector mounts, but they don't always deform.
If you have any doubt, replace them. Keep the old ones in case of emergency, though.
N
[BTW, the folks at Blue Ridge Diesel told me this... ]