1. A method comprising: determining, for each user of a group of users, a time difference between an event of a first type that is related to a storage of a user data unit of the user within a cache of a storage system and to an eviction of the user data unit from the cache, in response to (a) a service-level agreement (SLA) associated with the user and to (b) multiple data hit ratios associated with multiple different values of a time difference between events of the first type and evictions, from the cache, of multiple user data units of the user; wherein the determining comprises: checking, for a given user of the group, whether the SLA associated with the given user will be maintained when reducing the time difference; preventing a reduction of the time difference when the SLA associated with the given user will not be maintained after the reduction; and reducing the time difference when the SLA associated with the given user will be maintained after the reduction; and evicting from the cache, based upon the determination, one or more user data units associated with one or more users of the group.