If you're normally a continuous cruiser, you won't normally need a Galvanic isolator. But if you are spending time in a marina, don't forget that whenever your boat's hooked up to an electric point, you absolutely need to protect her from Galvanic currents.
Of course, this applies to ANYONE who plugs into an electric point, whether it's a marina or an on line mooring.
Galvanic currents can corrode your boats hull, prop and sterngear, and eat away at your anodes. And all this can occur a lot faster than you might think. Once the pitting starts, it gets under the syrface coating, and can be a lot worse than it looks. A Galvanic isolator STOPS this from happening, protecting your hull, anodes and surface coating, (blacking).
To fit a Galvanic isolator only takes a few seconds - you just plug it in. There's no wiring in needed.
For more info, and to buy, please.... 
