As Golddigger pointed out, lights not cycled can last way longer then the expected manufacture stated life, this goes for all lamps, as inrush and thermal shock are no longer a problem with aging the lamp, I have heard of T-8's lasting 3-5 years never being turned off, Thats 26280 hours up to 43800 hours, I have a truck shop with T-5 54 watt HO's that have been continued service for over 7 years and only had 3 lamps go out at about the 4 year point, on the other hand the lights they do turn off on a daily bases have lasted about the same to a little less which is allot less hours.
One problem with fluorescent types of lamps that use phosphorus coatings for luminance is even though they last longer they will loose luminance over time as the coating decays just like the older CRT type televisions did. they have gotten much better then the older fluorescents with using the special rare earth elements we now use in them, but the effect is still there.
also allot will depend on how clean the supply is, and the temperature extremes they will have to endure.
Most electrical and electronic load will have this same effect as thermal and inrush shock can shorten the life of even computers, incandescent lamps are subject to inrush current and we see this as most filament type lamps will blow right when we switch them on when the filament is cold and its resistance is low.
if you are going to be on your computer even as little as an hour in the morning then a few hours after work then its best to just boot it in the morning then shut it down when you go to bed or just maybe reboot it once a day but never shut it down, this keeps the motherboard and all the other parts at a more constant temp which goes a long way to helping them last, of course this also adds to your electric bill so in that case maybe just let it go into standby then reboot it once a day to refresh the memory or use a tool to clean out the mem of TSRs left over from programs no longer running.
About the only thing this wouldn't apply to is equipment that will have moving parts such as motors as putting hours on moving parts tends to add wear to them.
Also certain TV's and Monitors that use phosphorus screens such as CRT's, Plasmas, and DLP type technology can also suffer as the phosphorus coatings tend to decay over time as the electron gun beam hits them which is why a blank screen saver is best for standby instead of a moving image for these types of displays, LCD, LED, and TFT type of displays don't have this problem.
