I used multiple, got full offers pretty much same day (100pts@VGC). Didn't have to pay fees, but one broker was upset. But read the contract carefully, some brokers do want exclusivity.
Time on market will depend on what you are selling, how much you want for it, how many points and points available. For example, all things being equal you will sell a BWV faster than a OKW or SSR. But a BWV may sit longer if there are no points available in the current use year and all the points from the next use year are gone. Also, contracts higher than 150 pts sit around longer.
If you have points in the current use year and have not borrowed any points, it may just be your asking price.