There is no deadline, however immigration can make a decision at any time based on the information provided, in this case no info, as such they may deny the application.
The longer you wait, the higher the risk. That being said, it's unlikely to cause you a problem.
When you think of the cost and amount of time processing these visas take I dont know why you wouldn't want to get it sorted asap.
The longer you wait, the higher the risk. That being said, it's unlikely to cause you a problem.
When you think of the cost and amount of time processing these visas take I dont know why you wouldn't want to get it sorted asap.