D3 or a rock?

Here's the question:

I've been with my current girlfriend for about 3 years. Last January we moved in together after moving cross country. We get along great, etc... and she's pretty much "the one".

We are both pretty young (late 20s) and I'm in no hurry to get married - but she has dropped the hint several times. It's only natural - her clock is ticking!

So, do I make a down payment on a good sized rock for her finger, or do I get myself a D3?

Sure, a diamond is forever, but we're only here for a short time... and you're only young once.

Decisions, decisions.