It has always concerned me whether to boot and leave the disk running all day (or even permanently) or have the Humax boot on every recording or when I want to watch something. FWIW each day I usually leave my Humax in standby until I need it then rather than turn it off again I switch to a data channel eg. LCN 200 hoping that the strain on the time shift buffer is nil or small. Overnight it is in power saving standby - only because it is the last device in the aerial circuit (TV is old analogue and so aerial not needed). Of course, timers will upset this regime.
Not strictly relevant, but I did have a PC running 24/7 for the best part of 4 years for web serving and other uses with no disk problems. Also many years ago I was running a VAX system 24/7 with large simulation programs thrashing* the disk - no disk faults in 3+ years.
...I thought it was about the longevity of drives left running 24/7.