If there was one thing in Rainbow Falls that could be counted on, it was that no matter what disasters happened, Alchemiracles would stubbornly be open. When Nightmare Moon had returned and threatened to plunge the world into eternal night, the shop was open with a deal on night vision potions. When Discord had infected reality with his chaos, the shop was still open. In fact, Discord never touched the town, since Arca causes enough chaos there already. When Cozy Glow drained all the magic from the world, the shop was still open. Also Arca literally didn't notice anything since he has so much magic.
Rain or shine, hot or cold, it didn't matter. Open hours were open hours, and somepony was at the counter during those hours. The only exception were emergency schedule changes like being called to Canterlot on short notice.
Of course, just because the shop is open during a torrential downpour, doesn't mean any customers will show up.
Juniper poked her head out the front door of the building, looking at the dejected science pony laying on the porch. To make matters worse, Arca had chosen to mope with his head and front hooves dangling over the edge of the porch, meaning his mane was soaked to the bone, as were the collar and sleeves of his lab coat. Honestly, it was almost pathetic.
"Boss?" Juniper tested for a reaction. "Boss, are you okay? I know we haven't had a customer in five hours, but it's a dreary day. At least come inside and stay dry instead of waiting for clients?" She paused. Juniper stepped outside completely, draping a wing over Arcane in a gesture of comfort. "...boss?"
"...ZZZZZZZZ…"
Oh.
Juniper let out an exasperated sigh. This wasn't the first time she'd caught Arca passed out after an all-nighter, and it certainly wouldn't be the last. There was practically a list of places Arca wasn't allowed to sleep at this point. However, the wing across his back roused the alchemist, slowly blinking his eyes before proceeding to shake off like a dog.
"Gah! How long was I out? Did I miss a customer? Oh hi, Juniper. Why are you on the porch? I thought you were on register duty."
"No customers in the shop."
"Oh." That got his ears to flop down again, and he laid back down, thankfully fully under the overhang, and stared out into the rain. With nothing better to do, Juniper joined him.
"Hey, Boss?" Juniper hesitated, but the glance from Arca spurred her on. "...what's it like? Being ageless."
Arca stared back out into the rain for a minute before giving his answer. It was simple, yet raised more questions than answers. "Excruciatingly painful. But it's the best pain, because it's worth it." Another pause. It was rare to see him like this, all the crazy and hyperactivity melted away to reveal the seldom-seen wise pony who'd been alive for over a thousand years. Arca didn't move this time, continuing to stare into the rain. Staring at something unknowable.
"You know, I've had this exact conversation with every single one of my apprentices at some point. I remember each and every one of them, Juniper. For Celestia's sake, the Berry family has been like, a fifth of them, at least. And do you know how it always ends? Every single time, without fail, I have to sit and watch as they get lowered into a grave. Friends, apprentices, rivals, it never changes. And the pony I see in the mirror hasn't changed a bit in all that time.
"There are nine immortals out there, Juniper. Nine. Nine out of who knows how many millions of ponies there have been between Celestia and Luna's ascension and today. It's great for waiting things out. You remember that annoying pony who git all mad at me at last year's trade exchange?"
Juniper nodded. "You mean Emerald? Yeah, she's still in jail."
"Who?"
"I know who you are talking about, boss."
"Okay!" Arca nodded before continuing. "Anyway, even if that pony hadn't gotten in trouble, and was actively trying to kill me, all I'd have to do is run. In the end, I would still be here, and they wouldn't. But that same fact also means that every time I look at you, Juniper, I have to accept the fact that one day I'll be attending your funeral. And there's nothing I can do about it. And it hurts." A single tear rolled down the stallion's cheek.
Juniper said nothing. Arca smiled warmly as he kept talking. "But I do what I can. Make the most of the time I have with those I know. It makes moments like this special. I've got all the time in the world, so instead of worrying about every wasted second, I'm instead grateful for the moments others give up to be with me." Slowly, Arca got to his hooves, stretching. "...but we aren't getting anything done having a tender moment in the rain. Why don't we continue this discussion in the lab, while we cook something up? Whatever you want… just something worth remembering."
"...why don't we go flying?"
"Come again?"
Juniper spread her wings, hovering slightly off the porch. "You may be self-conscious about it, Boss, but the whole town knows you have wings, and we are totally cool with it. So come on! Let's go practice, Luna's been saying you should try flying more anyway."
"But it's a thunderstorm out there."
"So?" She hovered in close, almost touching her muzzle to Arca's. "You said it yourself: nothing out there in that storm can kill you, and I'm gonna die one day anyway. So why not live a little? If all you remember is spending time in the lab, then what makes today more memorable than any other?"
Arcane Catalyst stared up at the cloudy sky for a few moments. He was thinking… thinking in a different way. It was really rare that his worldview got challenged like that, but when opportunity knocks, you answer. "...you know what, Juniper?"
Two orange wings extended from hidden flaps in Arca's lab coat. "You're right. Let's go make today worth living for."
And so, two ponies jumped off the porch and took off into the downpour.