Not as long as 5 years, that is for sure! The new ones now I think are different. But, we still have the old-style brands and we are pretty good at turning them off. I would say approximately 3 years? Just a guess.
A 40W bulb in my outdoor fixture that I left on 24/7 burned for six straight years. I've had nightlight bulbs burn for years as long as I left them on. If I ever turned them off they would not come back on. So, I have three that burn 24/7. I don't like a dark house.
My grand parents have light bulbs that are sixty years old in their kitchen ........if they ever get around to putting them in a working light fitting ,I'm not sure how long they would still work for......:)
Back in the 50s, my grandparents had an old hand-blown clear glass bulb that had been used in a closet for an unknown period of time. As I recall, it had some other type of way of getting the electricity to it other than the usual 'screw in' system we use today. The house is still there, but it is no longer in the family.