How many times have you tried offsetting a set of faces only to get the error shown in fig. 1?
Most likely there are some faces that will disapear or will go through other faces during the offset. The actual challenge is pinpointing these faces and eliminating them from the selection. You do not have time for trial and error, especially when you want to offset a zilion of faces at once.
I feel your pain. I wish that SolidWorks would offer us the option to create a partial offset of all the faces that can accept the operation, or at least to highlight the faces that could not be offseted, so we can remove them ourselves. It is too bad that no such troubleshooting tool has been included in the Offset or Thicken Surface commands.
Fortunately, the Shell command has such a debugging tool. You can use the Shell Outward and, not only you will get a nice explanation of why the shell fails, but you can highlight the faces that are creating all the problems (see fig. 2 and fig. 3).
Even limited, this procedure can save you a lot of time. Of course, the workflow can be improved a lot and, for that, do yourself a favor and vote on these 2 Enhancement Requests via your Customer Portal:
SPR 523436: Thicken and Surface Offset features should have same failure diagnosis analysis as found in Shell feature
SPR 625706: If an offset surface command fails allow user to skip the failed instances and still create the offset surface for the remaining surfaces (faces)