This is one thing thats why i didnt participate a bounty that took 3 to 4 month. Because you cant tell if the ico is not scam except to those professional who know the scam and not scam. So it will be good if you participate in 4 to 6 week bounty
Actually you can easily check it by yourself by visitting the project website and check who is the team behind the project and how much is the token sold on the sale. Join the telegram group too, look at the activity on the group, if no one chat and only people joining telling "good project, etc" and no real talk then you must be careful.