What is the recommended time frame for a bounty campaigns?
Each campaign has its own time frame. There is no one single term. On the timing of the campaign bounty written in the rules.
Each ICO team itself sets the dates for an ICO and there are no recommendations for this, since this activity is not yet regulated by the states. In practice, in my opinion, the ICO term of an average of about two months can be considered the best. The duration of an ICO should depend on the state of the market. Now, for example, the ICO term lasts about five months, since it is very difficult for the ICO teams to collect even the minimum amount under current conditions.