Under normal use the only spokes that should fail will be ones with some problem.
If the spokes have been used for some time and the wheel has not had some catastrophic crash / failing you know the spoke which are in that wheels are not sub standard ones.
If they are the correct length to be reused they will end up close in tension to how they where in the last wheel so will not be experiencing any different forces
Think of it like this.
Under normal use the only spokes that should fail will be ones with some problem.
If the spokes have been used for some time and the wheel has not had some catastrophic crash / failing you know the spoke which are in that wheels are not sub standard ones.
If they are the correct length to be reused they will end up close in tension to how they where in the last wheel so will not be experiencing any different forces
In conclusion.
It's all cushdy.