I use my slow cooker a lot, but always on low all day so 8-10 hours usually while I'm at work.
Today I have put beef in Guinness in it but at lunchtime (as I only decided to make after getting home from shopping) and have put it on high. How long will it need? I have no idea, but don't want tough beef, it is always melt in the mouth soft when left on low all day