I've made many, many batches of beer without a mashout with great success. Although, I find I do get a little better efficiency with a mashout. It's not going to make better beer, but a mashout might save you a buck or two at the end of the day. It's a matter of personal choice. I can easily do a mashout on my single tier Brutus10 system, so I choose to do so, but that's just my choice.