Offloading tests to 3rd party will not help you ensure that tests run fast as they should.
Working too long on your branch will only make mergers more painful later.
We use svn and git, but the workflow is still local fast tests before even branches commits. No personal branches, only features, and update those often because they're not exclusively your silo. And commit/merge to head often. And head is the only place where you get the 2h integration test run. Because otherwise, you'd wait 2h after every branch commit (which we know nobody can do)