Another few factors to consider are competition, frequency, and area.

We planned to not go again until we had a deal to offer, but we plan to start going again, just not with the same frequency (we were going at least once a week and it got redundant with no new faces).

Increased frequency of walk throughs?

I'm not sure the frequency, though.

Attacking a smaller list with more frequency is the way to go.

I’m targeting negative equity properties but am not sure as far as white letters or yellow letters, handwritten or typed, mailing frequency, etc.

I think it depends on the frequency of your area.  

By knowing your market's frequency of transactions you can gauge where 1.  

The most important are frequency and substantiality of sales. 

That said I get nearly that level of frequency on my rental properties, however that is due to my Mom taking care of the things like filters and she always has some small project going in the yard or painting or what have you.