Definitely not! Your campaign might have been added to our delivery queue right after a number of larger campaigns and it may have to wait for those campaigns to be delivered first. Head into the Reports section of your account and if your campaign is still listed as Sending, then it is currently be deployed.
While your campaign is sending you can see the exact number that have been sent and review the reports in real-time as they happen. If you re-send the campaign while the current one is sending, your recipients will receive 2 copies of your email.
We're constantly evaluating our delivery server queues and add new mail servers to our cluster from time to time to ensure we get your campaigns sent as quickly as possible.