Spindle Maintainance

I've got a 2.2KW spindle that I bought from CNC4U a couple of years ago.

It has been running well and still does, but I notice it sounds a little rough, like the bearings need some care.

Has anyone some words of advice about how to do this?

My spindle looks like this:

Attachment 11569

If you search on Jonathan's posts I think he has shown one broken down to change the bearings etc ..Clive