I find plates easy to keep if they don't get damaged. I had a beautiful one for years, but one day I was messing around in the tank blowing detritus off the rocks with the outflow of a powerhead.... As I was doing maintenance, and I let it pump just sit in one place, it kicked up a sandstorm and covered the plate completely. Later that evening I realized something was missing from the tank.... MY PLATE!! I uncovered it and there was no visible damage, but the next day the skeleton was exposed. Many LPS can recover as long as they have a little live flesh left.... these guys tend to die if there is even a little flesh lost.