Are you have some sort of problem with water clarity? 600 ish is pretty common for CH here in AZ. Most people don't run into any trouble until 900 or 1000. Fill water is about 250 here as well. You accumulate CH because it is in your fill water, but does not evaporate. I tend to keep my Alk a little closer to 80 when the Calcium is high. Other than that, I just enjoy my pool I've been trying to keep track of the CH level of the fill water on a seasonal basis. If I can find a season where the water has less calcium, I'll probably just plan for a yearly partial water change timed to the lowest CH levels of the year.
My pool is 2 years old, never had a water change, started at CH of about 400 with new pebble-sheen. It has crept up to about 600 in 2 years time. As stated above, stay clear of the cal-hypo.