Had a similar problem years ago. It was amazingly simple to correct, and cost NOTHING!

I had a Beseler 67S dichro head that used the original quartz-halogen bulb for years until it died. Paid $25 for a new one that lasted only a few hours. Went back to shop to complain. They graciously replaced it gratis and then told my why BOTH had failed! Not a bad lamp, not a voltage spike (already reduced from 120 to 24V), but bad AC plug prong.

This was years ago before polarized plugs and before three prong, grounded plugs. We dinosaurs remember the old plugs had only two identical prongs. Each was made of bent copper, slightly separated from itself so that it expanded to meet the metal in the receptacle. Over time, the bend becomes flattened and acts like a single blade. When plugged into the receptacle it makes initial contact, but occasionally the contact is momentarily broken, then immediately restored. This happens repeatedly, sometimes very quickly causing arcing in the receptacle, which you cannot see or hear. Naturally, this is detrimental to the bulb and soon burns out the filament. The solution then was to separate the bent metal of each prong of the plug, and keep them separated. This I did and the problem never occurred again. Bulbs lasted for years. The salesman at the photo store was 100% correct.

I, too, have a DeVere, and it has solid plug prongs. If your plug prongs are folded copper that have been flattened, separate them with a small screwdriver. But since almost all electrical equipment today has either polarized plugs or three-pronged plugs, I doubt that is your problem. However, the wiring to your receptacle or the wiring from the plug could be intermittently defective. If you are getting unperceivable, split second interruptions of current to the lamp, you are shortening the life of the filament. Two things could be wrong. First, check for tightly fitting plugs, bad wiring in the receptacle, or bad wiring to or from receptacle. Frayed or cracked insulation could indicate old or damaged wiring and could be suspect. Inadequately spliced or poorly wirenut-joined wires also are suspect.

Second, and this is a long shot, check the ground. If non-existent or insufficient in the receptacle, fix it AND run a redundant ground wire from the enlarger chassis to a nearby metal plumbing pipe, bypassing the receptacle ground.

Barring any electrical problem in the enlarger (intermittent short or open), this could correct your problem.

Good luck and let the rest of the world know how you solve your problem.