Deore hubs wont have bearings or cones as good as XT etc. Obv depending on the background of the hubs they might be Ok or very worn, If the bearings are shot, it's highly likey the cones will be too & naturally the inner surface (cups) in the hub shells. If this is the case you'll never get them smooth again, though new cones & balls will make the best of a bad job.
Frequent re-greasing is the way to prolong hubs etc, waiting for 'play' to appear is too late.
Riding: Cannondale R800, Thorn Enduro-foco
Hoarding: Orange Prestige, Ozone Oxygen, 92 Klein Rascal
Totally biased, the best bikes in the world are: 90' Raleigh Mirage 91' GT Talera 92 Diamondback Apex 95' Mongoose iboc zeroG 97' Voodoo Erzulie