Christmas shopping is one of those times where when I see a great deal which I think would be an ideal gift there are more odds that I will buy the item first and worry if it was the right purchase after. The main reason is because during this shopping frenzy there are more odds that the item will be gone if you take too long.
As well, another factor is that most stores actually increase the amount of days that you can return an item in order to accommodate to people who need to return or exchange items. Example, people who got duplicate gifts or if they need to exchange a clothing item for a different size. Therefore, that is even more comfort that you can simply return it after.
Thinking about it, this can actually save you money if the situation turns out that all of a sudden the item you wanted is gone. Usually by then people resort to buying it from others that are reselling it at a huge markup.