In my experience, compact fluorescent bulbs generally have a five to ten year guarantee and generally do not last nearly that long. I always save the package (or at least the guarantee and anything it calls for, typically the UPC) and the receipt, and write the installation date on the base of the bulb when I install it. Whenever one burns out, I check the date against the guarantee; if it’s less than the guaranteed lifetime I put the receipt and UPC in an envelope and send them to the manufacturer, who usually sends me one or more coupons for free light bulbs. They cost as much as twelve bucks a package, so it’s worth the effort for me.
David D. Levine is the author of novel Arabella of Mars (Tor 2016) and over fifty SF and fantasy stories. His story “Tk’Tk’Tk” won the Hugo, and he has been shortlisted for awards including the Hugo, Nebula, Campbell, and Sturgeon. Stories have appeared in Asimov’s, Analog, F&SF, Tor.com, numerous Year’s Best anthologies, and his award-winning collection Space Magic.