Our SOPs:
Standby Altimeter to 1013 on passing 10000' or sector MSA, whichever higher. Primary altimeters are set to 1013 when cleared to a FL so SBY provides terrain reference whilst still below Transition/MSA.
SBY set to arrival QNH shortly before TOD, as in your new SOP. We complete Descent Chx before TOD; part of which is to set said SBY Altimeter to arrival QNH. This provides a terrain clearance gross error check during descent for the event that the selection of QNH on primarys is missed (it has happened!!). If a discrepancy is noticed between the two primary altimeters (whilst still above TL) then it is a simple procedure to reset the SBY to QNE and perform the required cross-check.