It totally depends upon the ICO team. Usually bounty campaigns offer stakes per week . For example if a bounty campaign says it has allocated 10000 tokens for its bounty campaign and the campaign will run for 4 weeks , then 10000 tokens will be distributed among the bounty participants in 4 weeks. As for the stakes, for example  if you are a junior member you will receive 0.5 stake per week. After the end of four weeks, bounty manager will add up your four weeks stakes. ie  0.5 stake X 4 weeks = 2 stakes. When the campaign end,just imagine  there are total 1000 stakes earned by all participants in the bounty campaign. So your tokens for four weeks will be calculated like this - 100,00 tokens / 1,000 stakes = 100 tokens per stake. Now you have 2 stakes, you will receive 100 tokens X 2 stakes = 200 tokens. hope you understood.