If you need more than 14 days, it seems a purchase upfront isn't the best idea to begin with. What would be better is to either borrow or rent it from someone/some place that already has one.
Making a purchase is very different from getting one to try. Beyond a 14 days return policy, you start getting abuse from people trying to exploit the exchange policy.
As many people say, 14 days is kind of a standard. Many companies have even fewer days so read the fine print before you buy. If you don't like the return policy, don't buy it.
If you absolutely have to have one on Day 1 but don't feel 14 days is sufficient, maybe evaluate why you need it on Day 1? Wait for some other people to have it in their hands, and the rentals/loans usually start a few weeks after launch.