is it fair to assume that since laptop have their own battery, one can safely setup primo cache with L1 write-back delayed mode since even an abrupt loss of power would just switch the laptop to the battery which (depending on the plan) would got to hibernation or shutdown gracefully before running out?
It should be just fine in that case. The only time your cache contents (and deferred-write cache) are at risk is when you encounter an ungraceful shutdown (bluescreen, unexpected power loss, etc). Usually even when a battery is old and barely has enough power to complete the hibernation process it will still complete, so your risk is minimal to nil.
Laptop with a battery is indeed better protected than a desktop from a power loss. However hangs and crashes still may happen. I have seen this several times and the only problem I ever saw were corrupted setting of the Chrome browser. If you are saving something important you may always use "Flush the deferred ... " button in the PrimoCache GUI.
