mIRC is not made with humans in minds, not bots. As such, most of the focus in implementing new features is on usability, not efficiency. The drawback is that the scripting engine is SLOW, so while you can make simple bots, it's likely to hit a limit once you start using it in extreme scenarios. If you need a program that is MADE for bots, you should be looking into eggdrops, mIRC won't help you. I'm not even going to bother asking your intentions for joining thousands of channels at once...
