curious I think that contracts (written or not) are binding and just like with any financial contract it is wrong to say you can cancel at any time.
If you rent a house and your contract states that you have a minimum rental period of 1 year and after that a 3-month notice period applies to cancel the contract, why should that be different from a contract about chastity belt wearing.
Because freedom, sexual or otherwise, is an unalienable right and cannot be enforced in a contract, exactly as a slavery contract will be null, a contract of chastity is null. You can't ask it to be enforced through the law. This is true in every Western country, and I suspect in the entire world. This means that even if someone signs the most binding contract, the one in chastity can ask for release immediately and there is nothing to do except comply, because if he goes to the authorities the enforcer will be incriminated, being the contract null.
The fact that you think that you can equal a property to a human fundamental right is something you should reason about.
The same will be a contract where someone sells his religious freedom. Null, no matter what.
This alone makes a chastity contract completely unbinding
But the most important thing is that offspring are not peers. A parent will (should) consider his son's well-being his most important priority, and if a pact makes his life miserable, and this forum is full of suffering inflicted by chastity, then no pact should be more important than this.