I can dig it.

Perhaps this headcanon will be ammended somewhat:
 
Due to Cadence’s powers (and the nature of her being an Alicorn), Shining Armor’s life will be extended by a few years, perhaps up to a decade longer than the normal pony lifespan. However, the rest of the headcanon remains intact.

Nice headcanon. It makes Cadence a little more tolerable - even if only because it means she will die after a few decades or so. It also makes sense for a Paragon of friendship or love to never have to fear the downsides of long life and watch the ponies who helped them there fade away.
 
I’m not too keen on the correlation between life expectancy and the ‘thing’s’ lifetime. I’d rather it be less strict so scenarios such as Twilight first passing can exist and allow storytelling opportunities involving the survivors. This is especially useful for exploring ideas on what would happen if Luna and Celestia were to cease to be.

so its pony Chrono Crusade.  
interesting.

@Lathius  
The pre-unificiation did it collectively. The princesses do it all on their lonesome.

Hrmm… pondering…
 
Naw, not buying. Cadence will live on as decreed by Hasbro.

@ClownDicks  
>Implying Celestia and Luna have cosmological importance.
 
Ordinary unicorns were raising the sun and moon before they were brah, they were even using it to extort the Earth Ponies.

I like.

@Cataclysmian  
Or, as “highest level unicorns”, they can easily do age magic.

This is a sad but impressive headcanon. Accepted.

something good out of /mlp/? I may just vomit.

Thats…pretty fucking rad actually. I buy it.

I was just thinking about this earlier today. It would make sense that an Alicorn’s lifespan be dictated by whatever exemplifies them; for the two that control the practically timeless sun and moon, that lifespan would be practically infinite. But for something tied to (a) mortal being(s), such as friendship and love, that lifespan would be of a corresponding length.

>implying Cadence has cosmological significance like Celestia and Luna do