I think vesting is a good idea for the founders (it's in their best interest), but I think if you're asking for someone to commit to such a long time period (ie 4-5 years), then it better be really good equity. Even better than if it were just offered "up front." There are also opportunity costs to consider, so your early employees or co-founders could be off starting their own companies with a lot more equity. So it's probably going to vary by each person, but in my experience, the vested equity has to be really good or I'm not interested.

I've been in startups where the vested equity was really low, and I left (I was employee #1). I've also talked with numerous people who thought about joining the same startup, and refused due to a number of reasons, but low equity was mentioned as one of the first reasons.