If you recalculate something, so that the something
doesn't stay in memory, it won't stay in the cache either.
The cache is a memory cache - what's there is also in
the main memory.
CPU's have become faster, but main memories have become bigger.
Nowadays, computers tend not to swap; if your server swaps
on a regular basis, you might want to do some tuning.
Memory I/O is faster than disk I/0, and the ratio
memory I/0 / disk I/0 is more than the ratio cache / memory.
Maybe not much of a data point, but from the servers with
resource problems I've seen, more of them benefitted from
getting more memory, than more or faster CPUs. Most computers
have more than enough CPU cycles - but usually they can use
more main memory.