The “post-acquisition” vesting periods have lengthened over the past years.
Acquirers these days typically want key founders to stay at least 2 years, and often 3.
This can often include “reverse vesting” of shares or other holdbacks that retain a significant amount of consideration (usually 20%+) unless the founders stay 2–3 years.
Many corp dev departments these days want 40% of the founders’ deal consideration one way or another to be subject to staying. This can be a combination of stay bonuses, re-vesting, certain escrow provisions, earn-outs, revenue milestones, as well as carrots like new equity grants, cash retention bonuses, etc.
Selling these days isn’t a ticket to retirement. You usually gotta stay. But sometimes it is a ticket to rest-and-vest. The conditions vary.