In the current implementation, additional work is done if a cache entry has already expired, but the cache is large enough to accept it. Consider the case when exceedsCapacity = false and entry.CheckExpired returns true. The cache first grows even if the entry has expired and then shrinks. It would be great in this case not to perform any manipulations regarding the cache size.
The approach I suggested would only change that expired entries won't be able to trigger cache compaction. (exceedsCapacity = true and entry.CheckExpired returns true)