Co founders agreement – milestone or time based vesting?

I'm starting a new company and signing a co founders agreement.

I feel a 4 year time based vesting is too much and I would just want to vest as soon as we hit half a million dollars on revenue ( in my head the business is now zero risk and growth stage and I have earned my sweat)

I also feel no need for a cliff since we have already both put in 6 months of work without pay and developed the product.

What am I missing?