Collateral should be used as a last resort for
bonding you would not qualify for otherwise. Usually, there are better alternatives than collateralizing a contract, as it lowers liquidity for you, which can ultimately increase the likelihood of a claim for the surety.
With that said, I suggest you apply with our agency, as we have markets that most do not have access to. You can do so online at: Contract Bond Applications - JW Surety Bonds
To answer your collateral question, it is held until the project is completed signed off. So the collateral would be held during your maintenance/warranty period.