I remove the nuts and washers, one at a time, clean out any bad stuff, recaulk, make sure the washer or backing plate is in good shape, then replace the nut and tighten, but not to full torque setting. After doing this with all the nuts, I go back and retorque part way on each nut at a time, like you're doing a cylinder head, until all nuts are at desired torque.
You should only have to do this every several years.
I've not done this on either of my keel boats. I'll have to think about it. I've only ever tightened the bolts using the logic that if the keel joint isn't separating and if it isn't leaking, why open a can of worms? On the other hand, my logic is flawed on several levels because when I've opened seemingly solid covers, dry walls, tiling, etc, etc, I've found stuff in desperate need of repair. Thanks for raising an important consideration.