The frequency of seal replacement on hydraulic valves depends on several factors, including the type and quality of the seal, the operating conditions of the valve, and the frequency of maintenance.

Generally speaking, hydraulic valve seals should be inspected regularly and replaced as needed. It is a good practice to inspect the seals during scheduled maintenance intervals, which could be every six months to a year, depending on the operating conditions of the hydraulic system.

If the seals show signs of wear or damage, they should be replaced immediately. Some signs that a seal may need to be replaced include leaks around the valve, reduced performance or responsiveness of the valve, or a noticeable decrease in system efficiency.

It is also worth noting that using high-quality seals from reputable manufacturers can help extend their lifespan and reduce the need for frequent replacements.