How important is resume continuity to you when hiring new sales reps? How likely would you be to hire someone with a 12+ month long gap on their resume?

Agree with other comments - it's highly dependent on the circumstances. Having just spent a non-trivial time on the market myself I empathize with people who are looking right now as it is a tough, slow moving market. Finding someone who is taking their time to find the right role (and can afford to do so because of prior success), using the time wisely to build skills, consult or focus on family priorities vs. someone who just jumps from one thing to the next might in fact be a much wiser choice.    

It depends on what they have done in the gap, travel is the best educator or caring for elderly or health impaired people is character building.

I'd evaluate the reason they were out of work, put them through our structured hiring process and then make an informed decision.  I've seen situations where an individual left their job to care for a sick child, a family member, or to handle an estate that turned out to be excellent employees. Don't lose a potential valuable contributor because you made a snap decision. instead do the due diligence.

Assuming they were a good fit for the position, it would then depend on why they were out for 12 months. One time, I had someone who had to care for a sick child. This person had a fantastic background, and I was happy to hire them and bring them back to the work community.