Hi Indy
Feeding away from nest, is partly not to encourage predators or unwanted visitors near to a nest box, and partly not to attract other potentially rowdy hogs, which a female might not appreciate right outside the door if she has young ones.
The distance really depends on your circumstances, so I couldn’t really give an exact distance, but if you know the reasons, you can probably work out the best place (depending on the layout of your garden, etc.) Hogs can walk up to 2 miles a night (males), so they need a bit of exercise to keep them fit and well. Hopefully the hogs are out and about looking for wild food as well.
