Since October last year I have been caching some of the old entries from users that had not visited the site for a while.
It allowed me to iron out a few problems with caching pages, (as you can set various privacy levels for all your posts), and it also proved to be very successful in releasing a huge amount of database resources, (trust me things used to be a lot worse than they are now!).
The site has a little less down time for an overall increase in traffic of about 50%, (I don't have the stats handy so you will have to take my word for it).
I have increased the number of cached pages, (currently in the region of 90 000 pages), in the aim of releasing even more resources that will enable things to run even faster.
That coupled with the new server coming up in the next few days/weeks and we should be safe for at least another year.
The numbers are tiny, on average a cached page takes 0.1s to be generated whereas a non cached page takes about 0.9s. This might not sound like a lot but seen that we are building a few thousands pages a second it helps a lot.
What I am trying to say is, if you come across anything odd, please let me know.