You earn commission on anybody’s purchase, except yours, if they use your referral link within 24 hours. One tip here is that you can trade referral links with family members and friends and use their link to make your own purchases and ask them to do the same so there can be sharing of the spoils. This might not be the major way to make money in the affiliate program Amazon runs, but it can help your commission structure.
One other positive about the Ultimate Bundles affiliate program that your readers may not have realized… They actually offer second-tier commissions too, meaning you’ll earn a share of the sales from any affiliates that you refer to the program. In this case, it’s 10% of their bundle sales during their first year as an affiliate which could be a nice earner!