Hello, can anyone please advise. 

Is there any guidance which provides info on when a 5839 system should be replaced or part replaced.  I have seen CIBSE part M which mentions - Fire detection and alarm systems 15 years  (Components include break-glass boxes, sounders, sensors, batteries, shutters, door fire curtains, exit detectors, smoke release vents, indicator and control panels and fire doors etc).

My thoughts are that some detectors and equipment may be subject to extremes of temperature and perhaps be in humid atmospheres in dirty dusty environments.  Some are in heated office blocks, flats, schools, hotels, care homes etc.  Is is normal to carry out such planned preventative maintenance at such a frequency even though the systems are tested weekly and have 6 monthly maintenance.  The system are not plagued with false alarms or issues.  If a catastrophic failure occurred a Plan B contingency arrangement is in place.  Do you think its reasonable to not have a fixed change date for i.e. panel, detectors, call points etc.

Many thanks

Most smoke detector manufacturers recommend the detectors be changed every 10 years.

Detector manufacturers actually have varying ages for warranties on detectors, some far more than 10 years.

A BRE study indicated that maximum lifespans shouldn't generally exceed 25 years for most devices which is  a fair amount of time.

The BS doesn't give a lifespan so as not to be used as a salesman's charter for replacing perfectly functional components.

Thanks for the replies I will have a read up on the BRE report.

https://files.bregroup.com/research/114408_BRE_Old_Smoke_Detectors_Briefing_Paper.pdf

Thanks for the link a very interesting BRE document on which there may be further research in the future.