Why would a business use something other than a 30 day last click attribution model? What's the advantage?
There are two aspects to consider here.
The first, and by far the fuzzier, is the logical path to purchase. If someone doesn't visit your site for twenty-four days, are they really starting their shopping cycle over again, or continuing the original one?
Do they remember you at all?
Knowing your customers' shopping cycle will allow you to tailor this to your vertical. A car is a more considered purchase than a t-shirt.
The second is correlating those early clicks with purchases. Are very long sessions more likely to convert than short ones?
If so, then a longer window is important--once again, this is common on highly considered purchases. However, if your products are not a considered purchase, it's common for impulse verticals to be effective with attribution windows as short as one or two days. If the presence of older clicks doesn't correlate with higher conversions, then those clicks didn't contribute any value, and can be safely ignored.
Testing is recommended, however you'll find that most sites will do most of their business within 72 hours of the first click, so the fringe behavior of long sessions doesn't really move the needle. Some very successful sites have run unlimited windows, and still found value in them.
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