The correct way is to replace the crush sleeve every time you unload the pinion nut. Some guys remove the crush sleeve, slide it onto a round pipe or used pinion and beat the crush with a hammer to extend the length so it can be reused, but that's not the correct procedure either. Some guys ,like baracuda pointed out, install a shim under the crush sleeve and reuse.
Just know this, if you don't take steps to place the proper preload on the pinion bearings with the crush sleeve, the tourqe applied to the pinion nut will place an abnmormal load on the bearings and bearing failure may result.
On the other hand, millions of mechanics have replaced the seals without ever messin' with the sleeve and without bearing failure.
Be aware that the rotational torque on used bearings is different from new bearings. Good luck and use an inch pound torque wrench to finish.