I posted this in Bicycle Mechanics, but noone reads that forum.

I was truing up my wheels last night, and I held on to the axle of my rear wheel and spun it a bit, and it felt a little 'crunchy', like as in not as smooth as it was when it was new. The hub is about 6 months old, and it's been seeing daily commuting duty on my fixie. It's a Formula hub, and the bearings are sealed.

Can anyone give my guidance on how I might be able to service the hubs to make them smooth again?
Is this something I can do with sealed bearings?
And also, should I even be worrying about this?
Any advice on keeping hubs in good condition?
Any help you can provide would be greatly appreciated.

Thanks!