In a typical ion exchange setup, there isn't all that much. A big tank filled with resin to attract the minerals, and a big tank of salt to wash the resin clean.

Eventually, the resin will break down and need replacement, or the valve on the tank will fail. But neither of those are insurmountable to fix, and will tend to last many years.

Now, if you go with RO, that's different. Then you really need a pump and multiple filters which need regular changing. Those can be a bit more maintenance. (Not to mention all the wasted water)