You shouldn’t be surprised if people sell tokens early if a project has no vesting schedule. 

Hope there is a lesson learnt with the drama. 

Implement vesting schedules via custody providers or onchain smart contracts. You can even have continuous vesting & it’s a great use case for blockchains. 

Industry standard is 4 years; not too uncommon to do 2-3 years.

Oh, and most importantly, cliffs are good to make sure folks stick around for a minimum period of time   

12 months is good :)