This paper explores short and long run economic outcomes of fixed label herbicide doses versus a flexible 'best efficacy targeting strategy' (BETS), which is factor adjusted to current weather and density of weeds. A herbicide efficacy model is combined with water balance, wheat yield, yield loss and weed seedbank dynamics models to construct a bioeconomic simulation model. Results with long run weather records from two contrasting rain fed wheat districts and a range of weed densities showed BETS was superior to static maximum label or half maximum dose rates at both locations, in terms of Hamiltonians representing mean net present values of current plus future benefits and costs of weed management. BETS also resulted in lower overall herbicide use, except in the case of the highest weed density where the half max dose was lower. These positive results raise the question whether such benefits from factor adjusting dose can be realised more generally, at other locations and in the cases of other weeds, crops and herbicides.