I’ve got two CFL bulbs in an enclosed kitchen fixture that were put in in May 2008 and they are still going. That light is on a lot each day. No one realizes they are CFL since the color match with incandescent is good.
I don’t use them for all fixtures, but for this one they are doing fine.
I have two wall lamps in a hall way, about 10 feet apart that have 100 watt incandescent bulbs that have never been changed since we moved into the house in December 1992. They get regular, if not “heavy” usage, on for awhile, off for awhile. They are G.E. bulbs and I’d be willing to sell them to the government to study if the price is right.
I really don’t have a clue why they have lasted so long.