Assuming you are using an apache server, you can refer to the Caching Guide (link), where some recommendations are found, such as this:
The default expiry period for cached entities is one hour, however this
can be easily over-ridden by using the CacheDefaultExpire directive.
This default is only used when the original source of the content does not
specify an expire time or time of last modification.
That is, you may overwrite the recommendation, but you should be aware of the files that will determine a longer expiration - and analyze if the reason is worth it, otherwise you may compromise performance. In the cited documentation, there is a part that speaks 'What Can Be Cashed?', where you can see more details about what you will keep longer.
You should also take into account the MCacheMaxObjectCount
(link), which determines the number of elements you will store in cash. It seems to make no sense, but at the time you will determine different average times for each file.
I know only one article that talks about different cache determination techniques, and you can consult it here.
I hope you’ve been helpful.
Apache? If yes, try this: http://answall.com/a/44178/3635
– Guilherme Nascimento