Currently all the motor currents are reduced to idle (default 30%) when they have all been idle for a while (default 30 seconds). It would be possible to reduce them to idle independently, and perhaps have per-axis idle current percentages.
I will be implementing standstill current reduction on the Duet WiFi soon, but probably not on the older wired Duets. This will allow higher motor currents.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].