For PC bulbs, its a good idea to change them every 9-12 months.
It depends on how often the bulbs are used. Tanning bulbs last a lot longer when they are not constantly on. Tanning beds in general are expensive to maintain. You will have a high electric bill and bulbs are expensive.
Not often if there tarting to wear and tear you should replace them.
comparing to the traditional light bulbs energy efficient fluorescent light bulbs uses 25% to 75% energy and saves money also and it lasts up to 3 to 25 times long so there is no need to replace energy efficient fluorescent light bulbs often.
It depends on the species, and conditions of the aquarium or pond
How often should you change water pump in a boat
Replace headlight bulb only when blown.
Light bulbs are often too high to reach, so stepping stools are used to add extra height in order to reach and replace light bulbs.
I've heard you should replace your pillow when you can bend it in half without it bending back.
A canopy is the cover that goes on top of an aquarium. Often times it will have a light built into it
The bulbs should be replaced as often as it takes to keep up their tanning power in the shortest amount of time. The average time is after 400 hours this is about the peak for the tanning power, however the bulbs can last up to 10,000 hours before they are innefective.
You might have to replace them once every season. Some burn out quicker than others, so maybe once a year if they haven't burned out yet.