Wow. This has almost completely hinted the ending of FiM. I never knew about this until now. Discord is immortal, except that Fluttershy ages.  
 
Face it guys. Fluttercord isn’t canon at all. They remained as BFFs forever. And they even became roommates too. I’m sorry. Fluttershy has aged for like 20 years. Discord hasn’t changed a bit, because he’s immortal, except his best friend.

Why do I do this to myself, read these fics and look at “immortality blues” pics…
 
@FanOfMostEverything
 
This. This is why. Excuse me, I need to dry my eyes now. *_*

@FanOfMostEverything  
I just read that, by the way. That was inspiring. I can’t right now. I just can’t.
 
You’re a beautiful, amazing person.

I couldn’t that. I couldn’t watch my friend die. I’m not now and I’ve never been that strong.

@Background Pony #0A78  
On her deviantart she added the wings derp

Those “mayfly” sadfics don’t make a lot of sense, they always feel a bit forced because they do not tell us the whole story. Did they had kids? Did Fluttershy had kids with somone? Did Discord made any more friends or had a love interest if wasn’t Fluttershy?  
Either way, both of them would had other living members of their family or their own children and grandchildren if Discord and Fluttershy did hook up with eachother or someone else.

Huh…Fluttershy became an Earth pony in her later years.
 
Either that or the artist done goofed.

“You never had to, you know.”  
“Grow old?”  
“It’s not a change I’m fond of. Especially not with you.”  
“I wanted to, Discord.”  
“So you’ve said. Even when the arthritis started kicking in. I thought for sure you’d be begging me to make you young again after that.”  
“Heh.”  
“… I’ve never really understood you, Fluttershy. Even during that encounter in the hedge maze, I didn’t know how to get to you. And now? Now your body is wearing out. Shutting down. How can you bear it? The meat supporting my friend is slowly dying. Why don’t you want me to do something about it?”  
“I’ve had to say goodbye to so many little friends over the years. It’s your turn, Discord. You’ve opened your heart so much. Now you need to learn how to keep going when it gets hurt.”  
“I am deeply uncomfortable with this conversation.”  
“Good. I was deeply uncomfortable during some of the most important moments of my life.”  
“I suppose it builds character.”  
“Mm hmm.”