what is a good ballpark figure to keep the hounders off?
I'd say somewhere around 5 hours per month.
Obviously don't so exactly 5 every month - some months 3, others 7, etc.
5 hours is low enough that they won't consider you for any "special privileges", but it's just above the typical "low hour mark" (maybe 2 or 3) that can at times set off a round of "shepherding calls" to "encourage" you.
Throw in 2 or 4 magazines per month, an RV or 2, and a book or brochure every 3 or 4 months, and you'll be golden.
You can write up your whole year's worth of service reports right now! Of course be careful that you only drop them in the box one at a time....