There is no limit as such on the number of campaigns you can create, send or schedule.

Though, remember that actual campaign dispatching is governed by the number of impressions left in your account. So if you have no impressions left in your account, you won't be able to send new campaigns. Similarly, if you have a scheduled campaign and at the scheduled time of dispatching you have no impressions left, the scheduled campaign will be paused and won't be dispatched...until you refill impressions again and re-send the paused campaign.