Keeping your disk around and in working order for a very long time simply takes a few routine chores to keep it going.
First off is cleanliness.
The worst enemy to your diamond disk is glass. "How's that?", you say.
Well, when you grind your pieces with your disk, particles of ground glass can build up on the surface of the disk. If allowed to dry onto the disk, these large buildups can prevent your disk from grinding. This buildup shows up as white areas usually around the edge of the disk. If left on its own, these deposits will eventually build up higher than the diamond, effectively causing your glass to ride on top of the ground glass instead of the diamonds.
The easiest way to prevent this is to take a jug of water and put it next to your grinder. After you have finished grinding, or even between every couple of pieces, pour some water over the moving disk and even rub it with a plastic bristled brush to wash away any ground glass that may have accumulated on the surface.
Once you get into this habit, you'll never have to worry about buildup of ground glass again and your diamond disk will last much much longer.