Plenty of Escondido homes have had a tankless on the wall for years, and most of the time nobody thinks about it. The first sign of trouble is usually small. Water that comes out a little cooler than it used to, or a code that flashes once and clears.
Those small signs are worth a call, because the cause is often building up inside the unit. Escondido's water is hard, and scale collects in the heat exchanger until the unit can't keep up. Caught early, a descaling and a part can carry it a lot further.
In bigger homes there's a second question, whether the unit was sized right to begin with. Someone comes out, looks at the unit and how your household uses hot water, and you get your options in plain English. You decide what happens next.
