It depends on the type and style of pH neutralizer you have. The maintenance requirements are as follows:
Backwashing neutralizers generally require backwashing (which uses around 100 gallons of water) every couple of days - depending on use.
Non-Backwashing neutralizers usually requires very little maintenance. You’ll need to add filter media every 6 months to 18 months depending on use and the size of your tank.
Vortech acid neutralizers need very little maintenance, other than adding media to them every 6 months to 18 months depending on use and the size of your tank.
Gravel bedded acid neutralizers require rebedding usually once every two years. And they require adding media to them every 6 months to 18 months depending on use and the size of your tank.