What i understand is that a draft agreement was produced last December,called the Backstop. There is and was no end date on this agreement. The next ploy by certain BREXIteers is to fantasise that this was time limited,. . It wasn't and isn't ,otherwise it would have been in the agreed text.
The difficulty all parties face is the fact that the so called "Government" of this country simply isn't the ultimate authority, it is effectively crippled by being Blackmailed, by gangsters that make Al Capone look Charitable by comparison, though they like him are involved in depriving the nation of Tax it is due.
Agreements with this non entity are a waste of time and effort, as they abandon them almost as soon as they are made.
There seem little chance of any other result than a no deal brexit jump off the cliff, and we will have to make the blackmailers face the music afterwards.
There is an old saying about Divorce
"The best way to punish a man who steals your wife is to let him keep her"
Brexit is a sort of "Divorce " we are told
The Leave camp illegally stole a victory to gain this Divorce
Brexit is theirs,, now is the time for them to make it work or suffer the consequences.