"Thermal expansion is a complete red herring in this case. That spanking new kit will be obsolete years before it's MTBF from thermal expansion."
Hmmmm, I have known thermal expansion push memory chips out of their sockets in a day. Every day. They had to be patted down by hand before trying to restart the machine (a Prime 400 for the techno-archeologists). Technology has improved since 1975 though.
If the machine is on every day for most of the day I leave it on, there are some house-keeping tasks set to run between 4 and 6am. File indexing, DB backups and so on.
'b