As a hiring manager, most of the time my mind is made up 30 minutes into the interview (though it's not considered polite to cut it short or notify them at that

As a hiring manager, most of the time my mind is made up 30 minutes into the interview (though it's not considered polite to cut it short or notify them at that time). However, in the very rare case of a tie, a follow up email (or handwritten letter) will definitely swing it in your favor. Actually, despite it being the common advice, they are quite rare to receive. So I tend to take notice and remember that person much later even if they are not selected. I would be likely to give the person another shot if they re-applied for another position, or pass their resume along to another position where I think they'd fit better. I'd never do that for someone who didn't follow up.