I have two Prime Hds on my 30 gallon mixed reef that is two years old. AI says the bulbs create usable light for 50k hours or about 5 to 7 years on average. My question is...Have the bulbs lost some of their intensity over the period or will they maintain their intensity and just fade out at the end? Should I increase their intensity slightly to compensate? I max out at high noon about 70% on a modified Saxby schedule. I have original par measurement I should probably rent a meter again, but anyone with thoughts or experience here?