I wanted to give a little historical context for Tony's age making sense before I continue:

Tony Stark first appears as Iron Man in a comic published in 1963. Unlike most comic stories where time in history isn't an issue, making for them to be replicable in the MCU in 'modern day' whenever that happened to be, Tony is tied to a stationary point in history due to Howard's link with Captain America. WWII is an unmoving point in real time and marvel time (comic and cinematic universes). Howard is an adult in 1944 when he works with Steve, Steve becomes a Capsicle, Tony is born, and then many unspecified years later after a ton of other events, Iron Man is born and the events of the MCU proceed. Howard in The First Avenger seems to be in his 20's or early 30's, which with other dates given for points would mean that he was in his 50's when he had Tony. That isn't super probable. Going off of RDJ's age for Tony's in the MCU, he would be 53 (at the point I'm writing this). If you shift Howard's age back about twenty years from the point of assumption that he had Tony in his 50's, you get his 30's, which is a lot more reasonable. That also would make Tony about twenty years older, in his 70's. I placed his birth year in 1946, making him 71 at the time of me writing this, because two years after Cap 'dying' seemed like a fair amount of time for Howard's life to get settled and him to have a kid.

So if you were interested, there's my logic for this piece. Now enjoy the non-analytical writing of it.

After working for another long, long time since his encounter with Steve, Tony finally ran out of coffee around the time of his 9:00 alert. He finished up some of his more sensitive work before grabbing a Stark Pad and the now empty coffee pot, taking the elevator upstairs to the common room and kitchen where no doubt most of the tower would be awake and ready to judge him. Tony was intent on acting just the same as (if not more capable than) before.

So, of course, the first thing he did was yeet himself over a sofa.

But he needed an excuse to do so. So pot and mug balanced in one hand and Stark Pad under his armpit, he launched himself, narrowly missing Natasha's head with his body, and grabbed an empty cup on the coffee table with his free hand. He held it up and waved it like a martyr for the rest of the room to see. Their attention had already been grabbed by his (quite small) stunt, and they looked, for the most part, like they were the ones about to have a heart attack.

"Seriously?" Tony started on his speech while sauntering over to the kitchen. "I emerge from my lair- don't tell me it's not a lair- to replenish my life juice, and you guys have stuff laying around? It's from last night, right? And still no one- you know what, I give up. Just show me to the leftover pizza. There better be some, Barton, that was our deal. And yes, I was conscious enough to remember."

Clint eyed him but bit his tongue for fear of the wrath of Steve. "Fridge, top shelf." He bit back every insult. The unusual empty, straight-forwardness wasn't lost on Tony or the rest of the room, and they suddenly all knew that Tony had heard then when he chose not to comment on it and grabbed his pizza instead. He nudged past Bruce who willingly made way for him to put the coffee pot back where it belonged and brew another pot. All eyes were on him. Most were careful, worried. Thor's were almost reverent. That freaked Tony out a bit.

He dropped Natasha's empty tea mug in the sink then leaned against the counter and bounced restlessly off of it with his palms behind his back against the cool granite. She was the only one who didn't seem to be paying him special attention, scrolling through world news on her phone and smirking (god that scared him) at some of the more violent headlines. Slowly, conversation faded back in, though it all felt stifled.

When the pot clicked to signal it had finished, Tony finally couldn't take it anymore. "I was watching the security cameras last night. Something very interesting happened." He said as pointedly as possible, coming off quite mad in the process. He met Clint's eyes. "I expect compensation for your nosiness."

Natasha slowly lowered her phone into her lap and risked a glance over. "It's not a big deal, Tony."

"Yeah? Okay. How old are you?"

She didn't break her gaze, but paused, tongue shifting in her mouth for a moment before she answered. "That's classified."

Tony huffed and rolled his eyes. "Doesn't matter anyway."

"Age should bring no shame." Thor declared sympathetically. Tony didn't respond, just brought his coffee down to the lab with him. He couldn't tell if his headache was from sleep deprivation, caffeine, stress, or all of the above. He had a pretty good idea.

In the common room, the atmosphere was left tense, but slowly settled. Steve hadn't come back yet from his run, so they had a chance to do something he might not approve of.

"Banner," Natasha said as affectionately as her training allowed,"You mentioned you were basically Tony's doctor. What can you tell us?"

He did try to decline, but if Natasha wanted information, she got it, and then the whole room knew all of his problems. Even Clint felt like this was going too far into his personal privacy. He listened with the rest anyway.