"Let’s try an another strategy then: bump as little as we can. This strategy worked much better."

Not sure this is a better strategy - it accumulates technical debt.

I think you should try to update as much as possible and stay ahead of the curve. That way you can reap the benefits of performance improvements, bug fixes and richer APIs. Sure, it makes sense to not use the bleeding edge, but being on the oldest possible version doesn't seem to be a good strategy either.