Depends on the cat (Baldrick wouldn't have gone far unless he was in a car when he went missing) but I'd probably go for a good mile radius if possible, if Mister tends to wander. I spent hours looking in the fields behind us, walked miles just in case - IMO better to do too many than too few.
I know it's hard but try not to get too disheartened by a lack of response - I nearly died of shock when I had a phone call from someone when Balders was missing but it turned out she was just phoning up to say she hoped he turned up soon. Which was lovely of her, but I'd rather have had a call to say she'd seen him.
Have you put posters up all around? It's worth putting up posters a long way afield.
Good luck, I hope he'll be home soon. xx