From what I have seen and heard it's about 1 to 3 years depending on how well you take care of it. At my home It's going on three years and going strong. Every 2 to 3 weeks I check the cell and clean it if needed. The first cell I had went bad after 9 months. It was replaced under warranty. They said that batch had a defect. Since then it has been great. I use an autopilot digital 36.
You should run a chlorinator every couple of weeks in your pool in order to keep it clean. Bacteria can grom in your pool and chlorine helps keep it clean.
It depends on how often you will be printing things out and what you are printing. If you are printing pictures, then expect to replace your ink cartridges fairly regularly.
how often should I replace the tires on my motorcycle>
A pool chlorinator can often be hired from the largest B&Q warehouses. They will hire it for a day or for a week if required. Alternatively a pool chlorinator can be hired from specialist pool suppliers online.
Not often if there tarting to wear and tear you should replace them.
You should replace your running shoes every year.
How often should you change water pump in a boat
Replace headlight bulb only when blown.
I've heard you should replace your pillow when you can bend it in half without it bending back.
Replace it when it becomes cracked or frayed.
Replace them every 100,000 miles.
Every 50k miles