Hi. SDW or it's account not required for LUN connectivity (also in a case of a reboot / failovers etc). It's only required for mounting new LUNs, removing them, and for backup operations running via SDW.
In case it stops working (for whatever reason I can't think of), you also do the add/remove LUNs directly from ONTAP, then format and add these to the cluster manually. With similar process from removing LUNs. And you can also still take non-OS/application consistent snapshots that will still be usable for 99% of the scenarios.