It seems to me that there is a dependency between Continuous Integration (CI) and build time. Each time I hit a slow build it puts pressure on 'fast' CI. It seems that if the build is slow then CI may be more destructive that beneficial. I'm thinking it is all a question of ratio.
CI does not define an integration rate. Some teams see CI as once a week, others see it as every 15 minutes. It is a relative concept.
If a build box can build and run all tests in, say, 1 second then a team's commit rate of once every 5 minutes would seem achievable. Each developer would have instant feedback and be able to fix, or revert, any problem within a couple of minutes, after a commit, with minimal effect (without considering a pre-commit test system). But if the build takes, say, 30 minutes and the team's commit rate was once every 15 minutes then by the time a build failure is detected the whole team is affected.
So it seems to me that there is a relationship between CI's rate and build time. Just do not know hat it is yet.