The pop/pvoice delay parameter was added long ago when disconnections were more of an issue. The purpose of the delay option is to stagger op commands so that they are not all sent at the same time. The delay is limited to a maximum of 15 seconds (versions.txt
24/10/1995 mIRC v3.72) and is randomized based on the number you specify. If you want to delay it for longer than that, you should use /timer. I will be updating the help file to clarify the purpose of the delay parameter in the next version.