Does the type of LEV system affect how often it needs testing?

It does, indeed. Though some processes are more risky and require more frequent assessments, the conventional maximum is every 14 months. Because of the amount of danger, LEV systems for respirable crystalline silica, asbestos, and welding fumes, for instance, might need to be checked every six months.
Therefore, the "one year" guideline is not always accurate. The architecture of the system, the hazard being controlled, and industry norms all have a role. Depending on your unique hazards, an occupational hygienist can recommend the appropriate interval.