If you kill the running operations manually, you'll lose the perfection of the stats/logs. So, for example, if you are running five threads with 60 hourly speed, the campaign will be fully paused after the completion of 500 emails which would take 500/60 = 8.3 hours. If you are doing warmups or sending emails at such a lower speed, you can always use the loop option while scheduling which will make you pause the campaign instantly.