OnePlus has extended the amount of time that its OnePlus 2 invites are good for, moving it from 24 hours to three days. The way it worked previously was you would sign up to receive an invite, and when it was your chance OnePlus would email you your invite. These invites had an expiration time of only 24 hours, and this caused a number of issues with potential buyers. Often times the codes were expired before the people even noticed they had it in their email, or before they had the funds available to purchase.
As a result of the feedback, OnePlus is now extending the length of time in which these invites are good for. Now, all invites will be good for three days, giving you more time to make your purchase before they expire.