There are only two factors that guarantee whether your capo needs replacement: tension mechanism and padding. This is primarily because these factors are the central feature that helps a capo perform its job.
In terms of tension mechanism, clip-on capos are usually equipped with a spring that applies pressure onto your guitar’s strings and neck. In contrast, slip-on capos utilize an adjustable knob to apply pressure.
Both types of capo also have their advantages and disadvantages. Clip-on capos are much faster to remove and reposition and are doable with one hand. However, their springs loosen up quickly. On the other hand, slip-on capos are much more durable and apply better pressure than clip-on capos. Still, they take time to remove and reposition and require the use of both hands.
The next factor to check if your capo needs to be replaced is its padding. Capo paddings are the material that has physical contact with your guitar parts and ensures that capos don’t scratch or damage them. Affordable and ordinary capos use rubber paddings, while premium and top-quality capos utilize silicon.
Rubber padding can imitate human fingers and help for minimal buzzing; however, they easily wear off and lose grip. Meanwhile, silicon paddings grip and clamp better onto your guitar and provide them with perfect intonation. This makes silicon paddings much more desirable in capos and far more superior to rubber pads. Its only downside is that they are more expensive.
Over time, along with excessive usage, it is only natural for your capo’s tension mechanism to lose its grip and its pads to wear off. When this does happen, it indicates that your capo needs replacement. You can tell that your capo is worn off when they don’t grip your strings firmly and when you observe buzzing sounds that weren’t present before.
Although there are available rubber and silicon capo sleeves on the market, it is still better to buy a whole new capo because it is tested by manufacturers to function as it should. A great piece of advice most guitarists would give you is to invest in a good quality capo that fits your budget. Although expensive, every penny is reflected in their performance, quality, design, and reliability.