Swamp cooler pads are vital in the proper operation of an evaporative cooler. The pad acts as a type of filter, allowing cooler air to pass through without getting water all over the place. Swamp coolers do need some maintenance, and replacing the pad is part of the upkeep.
1. Yearly Maintenance
Your swamp cooler should be checked for problems at the beginning of each season. The pad may not need replaced each year, but it's a good idea to at least check it. If the pad has lost its thickness, or you see fraying material, then go ahead and get a new pad.
2. Decreased Air Flow
If you notice the cooler isn't cooling as much as it has in the past, then the pad may be the problem. If particles get caught in the cooler pad, the unit won't function as it should. The cheapest thing to do in this case is to replace the pad. If this doesn't solve the problem you can move on to more troubleshooting.
3. Types of Material
Some pads will need to be replaced yearly, while others can last for several years. Wood wool cooling pads will need replacement less often. Some of the newer materials, such as plastic and melamine paper, may need to be replaced each season. You can check with the manufacturer of your current pad for replacement suggestions.