the nut for my front hub, wheel bearing assembly says "do not reuse nut"
is that because it is a lock nut and removing it and retightening it will reduce it's lockability?

 

If it's not a castle nut with a cotter pin, reusing it is not recommended. But should be okay for a few days while you get a new one. Just be careful.

 

I removed the nut and saw it is a nylock. I have been using nylocks on various things for many years and the more the nylock is tightened and loosened, the less locking grip.
Of course I reused it.
the nylon still had some grip but I used thread lock compound, so I don't think it will come loose.