If you understand that different shooting positions place one's eye in different places on the stock, variable eye relief can be very useful.
BTW, the latest 3.5-10x40, VX3's don't have nearly as much of this variable eye relief as the older VariXII's had. Eye box isn't quite what the older VariXIII's had at the lower mnagnifications, but it's still pretty good.
Where I've found a long eye box to be very useful is when I need to shoot in a hurry. Especially if my target is uphill or downhill from me. E
