Good for you!
Now you know what is inside and what to expect. And since you found a few dry bearings, how long to not go again. Or you had it done at the right interval and they did not put enough grease in. Dexter recommends every 12,000 miles or every year on grease repacking.
A few things I do to stay clean.
A. Stay ahead of the grease mess. Meaning when something get's all mucked up, wipe it up B4 going on. Clean as you go.
B. Old or new grease globs. I use old news paper as a receptacle. Meaning wipe out old gunk, either screw driver or finger and wipe it down inside the newspaper. Paper towels work too, just old news/junk mail adds are cheaper and work.
C. I do the dirty work, then clean up before installing anything. This way when you pick up brake drum or bearing it is clean to start with and you are not contaminating the new stuff.
I have been working on machines for the last 35 years and I do remember being a whole lot dirtier in the first few years. I still remember my mother telling me during the teen years, John what did you do jump in the grease?
Oh well guess I made it to being cleaner as time when on.
On the bearing inspection, this is what I look for:
D. Corrosion pitting, galling or any metal bumps. Look at the rollers and the races. You are looking for actual metal lose or high spots. Small pits, holes, bumpy surfaces. When new, the rollers and races are ground to a very smooth finish surface on 100% of the rolling surfaces. If you have a pit, soon it will get bigger in time and eventually lead to bearing failure. I'll see if I can find a few shot bearings to post pics of.
E. Discoloration or blueish color. This comes from lack of lube and high heat. When you start seeing the blue tint, heavy blueish or other distorted colors the heat has became high enough that it may affect the temper of the metal and the bearing life will most generally be reduced.
F. Uneven wear. You may not see any pits or rough metal but things should be wearing evenly. Look for burnished surfaces then high polished ones. This generally points to something not running true. If you see this you have to figure out what is not true or loose.
Good luck and glad the post helped.