I do not think there is a “stock” 1 size fits all answer…It will depend on your market, competition, prices, history, etc…
IMO 4 times in 30 days will annoy folks but it will really depend on how aggressive your competition is…You have to match or exceed the efforts of your competition…I think 1 every 4 to 6 weeks is a good range…
As far as offers, I would start with no offers or less aggressive ones and work your way up…When was the last time you delivered menus / magnets to these homes?..Maybe all you need to do is “wake” these folks up? While aggressive deals to seem to work, they are also hard to lose once folks get hooked on them…
Good luck…