I run 3 12k Reeflux SE 250s for 10hrs/day. I've been doing that for 6months, for a total of approx 1800hrs. Is it time to change them? I'm trying to keep my SPS growth steady, and want to change them before it reduces growth rates significantly. What is the rule of thumb you all recommend? In the past I can't say I've been very disciplined about this, but have vowed to change that. Thanks..