As great as the devfsadm command may be,
it will not always do everything that may be necessary.
Different hardware platforms, mixtures of vendor brand name hardware,
and different kernel patch levels can influence whether it accomplishes what you need.
A reconfiguration reboot will always rebuild the path-to-inst
and re-associate installed packages for new hardware.
A reconfig reboot has existed since before devfsadm was invented.
It just works.
Just go ahead and schedule downtime, and get the job done properly.