This is one question we get asked a lot at Intlvac. The short answer is ‘it depends’ meaning that there are a number of factors that impact the type and frequency of maintenance you need to perform. 

The maintenance intervals for a vacuum pump vary depending on ambient conditions and/or if aggressive media is involved. In a typical arrangement, clean application, we would say with confidence that 4-5 years of high quality operation is normal. After this time the pump performance may begin to deteriorate and you will lose vacuum pressure until the pump fails. It's important not to let the pump fail, instead it is wise to take it out before and have it overhauled. 

Before you reach the overhaul stage, take a look at your user manual to determine what the manufacturer recommended maintenance schedule is. For example, here is the outline for a SOGEVAC SV16: 

Use the schedule for your pump (will vary by model) as a guide and incorporate these actions into your daily, monthly and annual routines. To be relatively safe, at the very least, the exhaust filter should be changed annually (in a clean application). The oil should be changed every 3 months (in a clean application). 
Also consider the following:
•    clean the dirt trap 
•    check the anti-suckback valve 
•    watch the oil level to make sure it doesn't fall below the oil level glass bottom marking
•    run the pump with the gas ballast valve open with the inlet blanked off every month. This removes any impurities in the oil by allowing a small amount of air into the vacuum generator to help push out condensed vapours (namely water)
•    contact Intlvac for a repair and maintenance kit. 

If more than regular maintenance is needed, an overhaul would consist of a complete tear down, degreasing in a chemical parts washer, and reassembly with all primary components replaced with OEM genuine spare parts. All of the pumps we repair must meet the specs as if the pump were brand new coming off the factory line. We also provide 12 month warranties on all Leybold brand repair. During an overhaul, we replace all plugs, valves, vanes, exhaust filters, springs, gaskets, o-rings, any working part that wears over time. We also inspect secondary components such as the motor, rotor, end plates, and stator to ensure they are within their tolerances. 

Still not sure what your next step is? Contact Adrian at Intlvac for more information.