Imagine if this was how her life went. Becoming an aged Unicorn wizard still learning and loving her craft, and caring for that old tree-house and what friends are still alive.
Its nice to look back and remember that she used to be a unicorn, ya know?

This image is literally not the real deal. When Twilight is older, she’s actually a princess causing her to grow taller probably like Celestia.

Wtf those old pony tales for kids were doing in my library

Twilight’s face, she’s like: Wtf am I reading??

Oh balls, Twilight’s become so bored, horrified and appalled that she’s aged fifty years just reading it!

Aww, you wicked people you just don’t understand how it really works. Not that I expect you to in the first place. (I’m looking at you bronies and 99.997992188994% of the world)
 
If only you and your ancestors had chosen grace and obedience in your hearts to all of your fellow man in the gospel of old times. So much would have bettered in knowledge of all things of prelife, afterlife and of peace and equality for all in this world, but it has not.
 
I’m a latter day saint (The church of Jesus of latter day saints) and I’m glad I have almost all of those things to cherish and wonder in the restored gospel with my beloved mother and members.
 
The point of this comment you ask? Well, I just wanted to share it with you and that I will be incorporating those religious beliefs into my six saga slightly altered Crossover story’s, called “Galaxy Defenders’. MLP:FIM being one of those chosen, corrected and more down to earth fandoms in the 4th saga. If… I ever get around or have the skill yet to write it all down yet, cause it’s going to be a series of Movies, TV shows and Novels.

@toonbat  
Alicorn automatically means princess, it seems.  
The point is being an Alicorn does not mean immortality.  
Cadence is an Alicorn (and a princess) and she aged just like Twilight did.  
And even Celestia & Luna haven’t been established to be immortal, just very long-lived.  
Since a dragon’s nap lasts 100 years, its not a stretch to assume their lifespans are ridiculous even when compared to an Alicorn’s.

@Background Pony  
But she’s not only an alicorn, but a princess as well. Plus, it’s been established that age spells DO exist. True, she’s not yet at a level where she can perform them, but if ‘high level unicorns’ can do them, it’s hard to believe she won’t be able to in the future.

@toonbat  
Alicorn does not mean automatically immortal.

I’m a little confused. Spike is still a baby, but Twi’s old?
 
BTW, that’s by far the nicest-looking elderly pony I’ve ever seen. Too bad it will never be canon now, probably.

@JP  
yes, calm down and don’t so intolerant :P

What the shit are humans? XD

Calm your jets, JP. There’s much less religious pretense behind this picture than you think.

Put that down. Twilight, please, if there’s even just one book you don’t want to read, ever, it’s that book right there.