Can someone please help me understand what common re-vesting schedules are for founders? Like, if I raise seed money, surely I'll have to agree to a reasonable 4-year vesting schedule. But then if I raise a series A, B, and C, do I have to agree to new vesting schedules at each raise? Will I then not fully vest until 4 years after my series C? Do I lose all my vested shares at each raise? On the one hand re-vesting seems unfair to me, but on the other hand if I were to give someone 20 million dollars I wouldn't want them to quit the next day.
Also, sometimes you hear about founders being fired by their board. In this case, are they getting fully vested or are they just leaving with the equity they had vested at that point in time?
Some amount of re-vesting is often required at Series A, but it largely has to do with how vested the founders already are. If for example they've been working on the company for only a year, the existing vesting schedule will probably be left alone. On the other hand, if they've been working on the company for multiple years and are close to fully vested at Series A, it's almost guaranteed that the Series A investor will ask the founder to re-vest some amount of shares (for the reason you describe).
Re-vesting generally does not show up again after the Series A.
If you get fired before you fully vest, whether you leave with the equity you have or all your equity is something you can negotiate as part of the vesting terms.
Also, sometimes you hear about founders being fired by their board. In this case, are they getting fully vested or are they just leaving with the equity they had vested at that point in time?