I'm sure someone will default to old tank syndrome and the accumulation of detritus in the sandbed. To me, that's like an old wives tale... or should I say an old sailors story.
I just think that's just an old veteran who becomes a little too comfortable in the stability of his system and let's a parameter drift slowly, causing a crash.
I do not doubt though the possibility of nutrient loading in a system letting out a metaphoric grenade and tanking the system. I just believe it to be a small likelihood in our reef tanks.
Don't try to put words in my mouth!