Definitely not! If you are ready to lock your bounty for 4 months, then I am not ready to do that! I believe bounty shouldn't be locked in either way!
It is not ok to lock bounty for 4 months because projects should pay participants after ICO, doing some job no matter how small it is should be payed after job is done, company which doesn't pay for 4 months usually ends up on TV. I can agree on locking tokens for 4 months or until project goes to beta phase or released, but in investors and bounty hunters wallets.