Length of the bounty campaign is directly proportional to number of tokens. usually people looses interest in longer bounty campaign. It is also very time consuming. Best option is to participate in media campaign and try to avoid signature campaign, if the reward is good then join the campaign is last few weeks. I usually avoid bounty campaigns longer than 6 weeks.
It's a good idea, actually, to skip the signature. But six weeks is not that bad. Projects need participants and money to survive. Many projects with potential won't reach hard cap because they can't raise money in short time: people don't invest.