I really like the new northern brewee tall boy kettles .I currently do concentrated extract batches but im going to buy a bigger kettle to do full 5 gallon boils .Also I will eventually get into all grain 5 gallon batches but maybe 10 gallon batches (which are more common?) Should i buy a 10 gallon kettle or a 15 gallon kettle.If I buy a 15 gallon and only ever do 5 gallon batches is a 15 gallon kettle overkill?