OK by now the bulbs would have become loose, and yet they have not. I am therefore working under the theory that the excessive heat of 15W per bulb caused thermal expansion that caused the bulbs to back out of their sockets.

So there are now two benefits to using a lower wattage - longer life (still to be proven) and not coming loose!

Bumping to say still no blown bulbs and none of them loosening, none blowing. This is definitely the solution for those who have this type of lamp. Deal with a lower wattage and you are trouble free! (It is a yellower experience.)

Thanks for the update, Grotriman. So you are using the 6W lamps from the source you referred to earlier? I can deal with less brightness if I can get less heat.

Heat is the killer of incandescent bulbs. In the strongroom of my last workplace, we had an enclosed light fitting which would be on 10 hrs/day, and the bulb would blow every 6-12 weeks. I suggested to the maintenance man that we leave the cover off the enclosure - that bulb lasted for years.

Looks like an E-12, though you can check on http://en.wikipedia.org/wiki/Edison_screw

At LAMPS PLUS, , is http://www.lampsplus.com/products/ge-15-watt-exit-sign-indicator-light-bulb__91019.html - looks like the same size, but 145volt.

Ebay has a number of LEDs which fit an E-12, but they're all "fat". Not sure if you can modify it so they'll fit?

Correct! (Sorry for the delay I don't visit the forum often)

would you tell us where we can find those?

From a previous post: "Update - I found a source for these bulbs, relatively inexpensive at $1.28 for 10 or more, and also in a 6W version rather than the 15W. I'm working on the theory that less heat will make them last longer. (stock # B708106)

Added side benefit is that they cast a dimmer more yellow light in the same manner as Chopin's candles would have provided. Thus adding some more realism to my playing."

at Bulbs.com

http://www.bulbs.com/results.aspx?Ntt=B708106

That ad had the specifications, so I was able to track down information about an LED version here.