For the most part, the test suites on the Enterprise builders in buildbot-special run in the same amount of time that the normal builders take.

The sharding suite is an exception. For example, RHEL64 builder takes 1:40 to complete the suite; the SSL equivalent builder takes 6:34 (6.5 hours).
I think this might be a config issue, as most of the other special builders also take over 6 hours for the sharding suite, but some of them take "only 2 hours".