There was a Spike story I read once, and am trying to find again. I believe it was a Sparity romance, but I'm not 100% sure on that.

In it, Spike and Rarity have the following conversation (paraphrased from memory):
Rarity: But Spike, don't you have any ambitions beyond just being Twilight's assistant?
Spike: Do you know how long dragons live Rarity?
Rarity: Well no, not really.
Spike: Celestia told me we can live thousands of years. If I'm very lucky, I'll get to spend a hundred years with Twilight. I plan to enjoy it while I can.

If anyone else remembers it and can point me to it, I'd be most grateful.

3375329 You mean aside from that folder full of Spike stories we have here?

3376445 Why are you leaving?

3376445 Well okay then. Take care and thanks ever so much for bringing your pointless diatribe into my thread before you left.