I'm not a lawyer, but I think it's unlikely that this browsewrap agreement is enforcable in United States as the website doesn't ask the user to actually consent to Terms of Service, see Nguyen v. Barnes & Noble, Inc. (763 F.3d 1171).

What's the duration of this contract?

bullshit Shrinkwrap contracts reduce the choice of all of us internet users. this website has was made to poke fun of the current state of contract law. enjoy!

Before I saw that this comment was OP, I read this as "Bullshit, shrinkwrap contracts reduce ..." which I thought was strange since it seemed to be broadly agreeing with the point of the site.