This brings up another issue:
What you need to be careful about is merchants that are using "local tracking". This is basically used by merchants that use multiple networks which is becoming more and more common these days. In a case where local tracking is being used by a merchant, the merchant's site will only show the 'last referring' networks tracking code. Without going into great detail of how it works, the networks and the merchants responsibility is to check that the local tracking is working correctly.
Some problems that are common:
1. The merchants local tracking only works "in session" and not for the cookie length. Which means in your example above, returning to the site in 2 weeks would result in you losing the sale.
2. The merchant needs to set the local cookie for the same time period as the affiliate network advertises (sometimes the length doesn't match what's advertised).
3. In the event that the customer deletes their cookies and therefore the merchants site cannot find a last referring network; all networks tracking codes should be displayed to ensure that a potential sale is rewarded for any network using "cookie-less tracking". Like Webgains
You shouldn't have to test this stuff yourself as it's the networks responsibility to ensure the merchant is well advised. However, I can assure you many merchants in this industry do not have (whether deliberate or not) the correct setup. In fact, many of our merchants that have come from a multiple programs setup have had the incorect setup and thus have been not paying affiliates since their affiliate marketing campaign started.
All of our merchants go through stringent pre-launch testing period if local tracking is in place to make sure that the local tracking is working correctly. Not only that, but constant random testing should be done by the networks to ensure that any of the merchants "site updates" have not effected the tracking.
Maybe we should have a "local tracking test - approved" symbol on the relevant programs to keep you informed?
