There was a generation of LectraSan EC that had short lived electrode packs...but that problem was corrected when the MC model came out. When maintained and care is taken to make sure it's getting enough salt and power, an electrode pack should last at least 5 years, even for live aboards.

And Dave.... Warm waters have such a high calcium carbonate content that it may be necessary to clean the system 3x/year or even 4....but a weekly cupful (any more is wasted) of white vinegar down the toilet not only prevents mineral buildup in the toilet pump and head discharge plumbing, but it also reduces buildup in the LectraSan/Electro Scan. And it can stay in the system indefinitely...just don't leave it sitting in the bowl unless you want to replace the joker valve in the toilet weekly.