How long will he stare at me for until he says something?

As a single guy, I'd say until he ever has the courage/guts to talk to you and not worry/overthink what your reaction will be when he does talk to you.
I'm about to turn 33 tomorrow but when I was a high school junior, there was this beautiful girl I would stare at in one of my classes. It was a math class mixed with sophomores and juniors.
She knew I would be checking her out at times in class and smile back at me.
However, I just never bothered to talk to her.
It wasn't until back in 2008 when I was working in a grocery store and she ended up working at the coffee shop next door, that we ended up talking.
I ended up talking to her because she was a barista/cashier and she remembered me.
She would walk inside my job and say, "Hi," to me.
She likely no longer works at that coffee shop. At least, she was nice back to me.
As a guy, it's very nerve-wracking to just go up to a woman and just have a normal conversation.
There was a girl back in 2012 who was the most beautiful red-haired girl I ever saw in person.
She knew I was checking her out at times and would smile back at me.
I ended up writing her a note and giving it to her.
Well, I told her I "found" a note.
The note said that she was the most beautiful red-haired woman I had ever seen and maybe I'd talk to her the next time I saw her around.
The next time I saw her around, I overheard her talk about me to 2 of her female friends and one of them laughingly said, "He's a stalker!"
This girl who I wrote a note to, ended up walking right past me to talk to a guy she didn't know and asking him questions about himself when I was by them.
I ended up going up to her and apologizing for the note and she told me this, "It was a little strange but don't worry about it" and then she just walked away from me.
She didn't get that she was so beautiful in my eyes that I would be no nervous to just be normal towards her.
I was 27 back then when I gave her that note.
I guess its a "kid thing" to do by giving her that note but I never gave any girl a note when I was a little to even when I was a teenager.
I've had girlfriends and been on dates but it's definitely not easy for me to just talk to any woman.
If you're fed up with this guy, then move on but if you really want to talk to him then you're going to have to talk to him and tell him it's okay that you get he's nervous around you.
I hope that I've helped answer your question and take care of yourself. I mean it. ~Alan

Obviously, he's always liked you, but maybe he's grown braver this year. Tell him, "This not-talking is ridiculous. Text me. 123-4567 (your number)." Or pass that to him in a note, if it's too awkward.

If a guy stares at you, it clearly means he likes you. But at the same time, he's really really shy. This used to happen to me, and when I tried approaching him, he stepped back. He didn't stare at anyone but me, and when he stares I look back and we maintained eye contact for literally almost 10ish seconds!
His aim was to make eye contact with me, so he'll never look at me when I'm not watching, he only does so when he knows I can see what he does and thus, I can respond by staring back.
I ended up falling for him, because it really felr magical when we stare into eachother's eyes, it's like the most beautiful thing that could ever happen. We're both really shy and conservative, so when I tried making a move, he took a step back. I know for sure that he liked me, but again, I do know that he is really really shy.
This guy likes you fur sure, but if he's not making a move, he's really shy. If you approach him and he steps back, he's only doing that because he's shy, not because he doesn't like you.