Before a variety is released for adoption by farmers in a region it is subject to comparative field testing. An economic issue is how extensive and prolonged should be this field testing within the region; over how many locations, years and with what number of plot replications should testing occur? This paper addresses this issue for the main broadacre crops grown in Western Australia and shows through sensitivity analysis how robust are the findings for each crop type. Findings are contrasted with those already published for southern New South Wales.