Do they blowout or lose effectiveness? I hope you are taking them back if they are the mercury vapor bulbs I think they are suppose to last 5 years. Also many manufacturers suggest a 10 inch dome. If what you are saying is true then I might be in trouble. I purchased a t-rex mercury vapor 100 watt spot so far its been working well but Ive only had it for going on 2 months . Maybe if you got them at the same spot its a bad batch check the lot numbers. PLease post your results. I went to mercury vapor because its so much more convenient but if its going to be that much of a headache ill go back to flourecents.