I just thought it's ironic because mailers are the complete opposite they want constantly fresh offers and creatives and burn them out pretty quickly.
Sad but true. The problem is, we have a finite "base" of leads. Let's say a mailer has 500,000 "biz opp" leads and gets maybe 1000 fresh leads a day. Those 500,000 will become saturated from mail drops relatively quick, and the 1000+ per day coming in isn't enough to warrant a daily drop to garner some extra sales. So, you wait a bit, and when the count is more substantial, you drop the offer again. Rinse, repeat for your top 20 offers and you've now got a reasonable system in place for making money the email way.
We have to deal with attrition as well. Those 500,000 leads become 499,000 day 2 from optouts, etc. and new data needs to come in at a higher rate to maintain your metrics.
Whereas in Search, the world is the limit, and there is always fresh blood looking for your ads. So I can totally see your point how a killer offer can literally work for itself and keep you happy really, forever, or until break-down occurs.
I know that our biggest offers cap on volume a lot and will redirect randomly though the day. That's because the advertisers merchant accounts just process anymore.
I couldn't make a living with that unfortunately. Mailers plan their drops strategically at various points of the day. I'm surprised you don't get a lot of complaints from people for that, esp. high volume search people who are paying $3-$5 a click and getting redirects? But I'm assuming you tell them in advance what the cap is, and assign a cap to each client so they can monitor their lead and back off accordingly. To be honest I'd rather invest in an offer without caps so I don't have to worry about the door closing during a profit-run.
Great points all around, however, keep them coming.