Currently in the bidding phase of a new pool project. We are going for a salt water pool with flagstone coping and moss rock waterfall. Have been given conflicting info from the two PBs we have met with so far. First PB says sealing of the flagstone and moss rock is required initially and every 3-5 years. This is consistent with everything I have read on the subject. The 2nd PB states that sealing is only required if you don't maintain your pool chemistry properly. He says if you stay on top of it and hold PH at 7.4 there will be no scaling or pitting of the flagstone. My tendency is to take the cautious approach and seal whether it is actually required or not, "just in case".
What's the real story here from those that have had good and bad experiences in this area?