Should I worry if a broker wants a much longer listing period than I expect?

Not automatically, but it's worth asking why. A longer listing term isn't inherently unreasonable — some brokers genuinely need more time to properly market a business, especially in a specialized industry with a smaller pool of qualified buyers, and a term that's too short can undermine their own ability to do the work properly. A broker who explains their reasoning, and ties it to a real marketing plan, is in a different position than one who simply wants a long commitment with no clear justification.

What matters more than the number itself is what you're getting in exchange, and what your options are if things aren't working partway through. A long term paired with vague marketing promises and no meaningful early-exit or review provision is a combination worth pushing back on; a long term paired with a detailed plan and a fair mid-term check-in is less concerning. Ask the broker to walk you through why they've proposed that specific length, and don't be afraid to negotiate it down or add conditions. A Treadstone business lawyer can help you weigh the term against the rest of the agreement.