I have ILR, so I'm not sure what the procedure is for those arriving as visitors. Even those with visas have to fill out the landing card, which is slightly strange for this particular question--I just ended up writing 'indefinitely.'
In any case, I think that it will be the same situation as it was before when you were simply asked how long you were going to stay in the interview. If they don't think it's a problem, they will just give you the standard stamp. If they believe they have a reason to, they will give you a shorter leave of entry. I don't believe they are only giving you the amount of time you ask for, and haven't seen anything on this board to indicate that.
I just wanted to put it out there so that people won't be surprised when they see it.