The question I have presented here does not imply an old traditional development model where you keep working on something for years and then release it to the public. You can use agile or whatever model deem appropriate to you. The question is about What would you FOCUS on for 5 years even if you don't see a light of success and keep working on it.

Isn't the problem with Hurd the fact that they did spend years working on it, instead of just releasing something early and iterating?