If you're going to replace the wheel cylinders, make sure first that the adjusters aren't frozen up. If they are, you will be better off with a pair of new backing plates all ready to go, although you can buy new adjusters separately. I will just extend the threads of a new adjuster and coat it with a good marine grease, after doing that I have never had one freeze up on me.
With the wheel cylinders what you can do before installing them is peel back the rubber boot, put a bit of silicone brake grease (Permatex orange stuff) on the top of the brake piston, and seal the boot to the cylinder with hi temp RTV. This will extend the life of them and makes then less likely to seize up due to water getting past the boot.
The only problems I've had with drum brakes over the years were the wheel cyls and the adjusters, doing what I have written above, has extended the life of those parts by quite a bit.
The new Tiedown/Dexter 12" units I put in last year have a new kind of bootless wheel cylinder design that is supposed to last longer, I'll see if they last longer than the boot style. I always have one pair of backing plates in the garage, if I have a problem these can be swapped out easily.
I know some have had trouble with Tie Down actuators but I've had the same one since '04, still working fine, I have a rebuild kit in the garage if it fails and new emergency cable, if I have a failure I can be back on the road in a few hrs.
