I - the general 'rule of thumb' (but can vary from country to country) tends to be a 5-year shelf life for 'primary' research findings. For seminal, historical, theoretical, conceptual etc articles - the shelf life is variable. I think that your measure is more likely to be seen as a recommendation for student articles - and perhaps Honours theses. It may be viewed that it is best to 'restrict' such students to a manageable year range - so as not to overwhelm. However, for say high quality journal submissions and PhD theses, it is anticipated that the author/s draw on a broader range of literature over a longer time period - to identify both the past and current context. Quite a lot of my earlier work (often theoretical) , i.e. 15-20 years old, is still regularly cited.

In research activities, the reference used is the maximum publication of the last ten years. whereas for theory, has it also been the same for the past ten years?

Not necessary. Reason being some theories might be classic ones that you can branch out from there to add value for your research / conceptual framework - hence you might refer to those old theories that might be > 10 years (but you need to support this with your rigorous literature review effort)

Personally to me - relevancy in the right context of the theory is more important that its age.

Does knowledge get old? The purpose of using latest work is to see what new has been done. If there is latest theory which can be replaced the old one, then you should cite the latest one.

A good mix of the old and the new is alright. Articles within the past five years are regarded as new and should dominate research article references. Actually, a

Dear Dean Whitehead , Han Ping Fung , Muhammad Farrukh , and Maurice Ekpenyong :

thank you very much for the explanation. a very good input for me. Regards.