I think to participate until the tokens are not more expensive. Thanks to the developers for the bonuses.
At the moment it is a good option for investing. On this need to be resolved in the near future
Now a lot of the high-tech and fintech startups bring great profit. And earlier participants in the ICO have the more profit because they have the biggest bonuses.
Sometimes seed and early investors are real devils for projects. They get 30-60% discount and when tokens are listed on exchange, investors sell them and dump the price. So do bounty campaign participators and price falling get doubled effect.
But it is not always so. This is only if early investors are in a hurry to invest money in another project. Very often early investors just believe in the project and will hold it.