ShareAsale.com one very nice affiliate network that provide datafeeds and have over 2000 merchants waiting for affiliates to promote their programs now offer cookie return day statistics, that tell you how many days after initial visit the deal was closed... that's especially interesting for those that tend to promote more complex products or are just curious how long the period between initial visit and final sale is...

I found one client buying after 15 days... - ok - but most of them got their stuff immediately :-)