Hi There
Unless specified within a particular standard to which you are operating, I would suggest this is really just a matter of preference - with 'pros' and 'cons' for both having and not having an expiry date.
Just some thoughts, which may help:
1) if your documents do not have an expiry date, there should still be a documented procedure for checking both their validity and performance (on a predetermined frequency and to a schedule) - which is usually within internal audit systems.
2) If you produce documentation, specifications for example, that are for seasonal, or non-regular use, it may be worth having an expiry date to act as a trigger to revisit specifications / documents that have not been used for a while.
With Expiry Date:
documents may be revisited and reviewed more regularly - PRO
documents that don't often change still need revising - 'unnecessary' use of resources (time, paper, ink) - CON
increased chance of 'out of date' documents being available, or worse used, at an operating level (especially if there is not one central issuing hub) - CON
during an audit there 'will' be an OOD document found - lost confidence in document control? - CON
Hope this helps, or aids discussion.
Stuart