I have the LPL VCCE 7700 enlarger and noticed over the last few months my exposure times are getting longer. Today I went in to print and it wanted exposures up to 6 and 7 stops. That's ridiculous. I checked the lamp and it's seated properly. I just got the enlarger new about a year ago. How often do the lamps need changed? Why wouldn't they just burn out like any other bulb? Also, could it be the power supply going bad? The paper and developer were both fine. I'm hoping changing the lamp will be the quick and cheap fix, but I'm worried it's something more. Advice?