Frequency of Emergency Lights Certificate for communal Hallway in small block of flats?

Maintenance

So we have had the electrician give us a certificate for the Emergency lights last year.

With our HMO we do this yearly along with smoke alarms. However this building in Manchester of 4 flats is not a HMO, The Emergency lights are in the communal hallway. I am trying to find out what the legal requirements are for the E.Lights in terms of how often a certificate should be issued (not how often a test should be done). The standard response online is yearly tests but with no reference to what the rules are in regards to certificates. Testing it yearly makes sense.

Do I even need a certificate? The test requires to turn the lighting off and check the E.lights are still on after 3 hours. Could I not simply log this in the log book. I could even take a dated photo or video.

I understand that for some landlords checking all their properties and keeping logs would be difficult and it would be easier and simpler to pay an electrician to go around, and this would also prove they are doing their due diligence as a landlord.

The question arose when someone asked me isn’t it every 2 years? I know the EICR is every 5 years.