Anecdotally what I typically see is a big chunk of change over 4-5 years and then smaller chunks every year to extend the handcuffs. YMMV

It's quite a long time ... I guess many entrepreneurs just want to move on and hate being on the "you are behold to us" part of the acquisition...

I can kind of understand both sides. Company I used to work for bought up a small company to expand their product portfolio. I don't know the details, but the acquired company was never really happy with their new life and 2-3 years later almost everybody from that acquisition had left (and taken some of their new colleagues with them) and there was no one left in the company that could really continue the work they'd been doing. Basically 3-4 years later it was as if the acquisition had never taken place

My handcuffs are for three years.