A shorter term gives you an easier exit if the relationship is not working, but it can also pressure a house onto the market before it is properly prepared. A longer term gives more room for a slower selling season, at the cost of being harder to walk away from quickly.
Ask specifically what happens if you want out before the term ends: whether the brokerage will release you in writing, and whether any marketing costs already spent become payable. That clause matters more once a home inspection, typically $400 to $600, has already been arranged and paid for.
The length itself matters less than knowing exactly how you get out of it if the fit turns out to be wrong. Get your hand-reviewed valuation from Joel Dyck.