There is no general answer to this one, but I'd say those 6-12 first months are when the company is most derisked. If you're going to be employee #1 of a 12-months-old startup, it means it still exists (vs all those failed projects), so it is much less risky, and founders are compensated for this risk (don't forget that in most case, their huge share of equity will be worth nothing in a few years!).
Of course once employee #1 joins he usually works as hard as the founders and I understand if he wonders why he got so little equity but those first months are more crucial than appears.
Let's take the example of the company I'm cofounding (tldr.io). When we started 10 months ago it was nothing more than a crazy idea with a very low chance of success (summarizing the web). Fast forward to today. We're still not ready to hire but we're getting close. The crazy idea has become a "there actually is a chance, although small, that it will succeed". I feel that the difference is huge.
Of course once employee #1 joins he usually works as hard as the founders and I understand if he wonders why he got so little equity but those first months are more crucial than appears.
Let's take the example of the company I'm cofounding (tldr.io). When we started 10 months ago it was nothing more than a crazy idea with a very low chance of success (summarizing the web). Fast forward to today. We're still not ready to hire but we're getting close. The crazy idea has become a "there actually is a chance, although small, that it will succeed". I feel that the difference is huge.