How long should a contest run? There’s no single answer here. The longer the contest runs, the bigger the reward needs to be. You’ll have a hard time keeping the sales force pumped up for a year if the grand prize is a blender.

Also, a long term contest (the longest I’ve ever heard of is a year) requires lots of effort from management to keep promoting it. Often, contests start out with a BANG but fizzle out because everybody kind of forgets about it: the day-to-day routine takes over.

On the other hand, if a goal of the contest is to change behavior–for example, to make three cold calls a day habitual for every rep–running it for several months makes sense. If the contest is designed to promote a brand new product, chances are it will take a fair amount of time to generate sales no matter how energetically the sales force works.

Short contests and spot bonuses are not great for changing behavior, but can really build morale and break up the routine. (These also work spectacularly well for non-sales departments, incidentally.)

Bottom line: be clear about what you’re trying to accomplish, and the question of contest length should answer itself.