If its an adjustable, ball bearing hub, then the proper adjustment is absolutely NO play. It doesn't matter if you can feel a little resistance when you spin the axle by hand, it will not affect the riding at all and will not affect the life of the hub, in fact, hubs last longer when there is no play in the bearing than if there is play.
I know, we all want the wheel to spin with no apparent friction, but don't worry about it. A little friction is ok.
Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1