It depends by topic. For example, one of the seminal articles on the Historia Augusta goes back to the late 1800s. (I'm on my phone right now, but later today I can add a complete reference.) In other areas our understanding has been changing dramatically. For example, our discussions of Pagans vs. Christians in Late Antiquity has changed from conflict (cf. Momigliano, coming later) to more or less peaceful coexistence (cf. Ed Watts and Alan Cameron).

If by Brown you mean Peter Brown, he's still one of the most important historians of Late Antiquity and still publishing books. You can never go wrong by reading through Peter Brown's work. For example, his biography on Augustine has yet to be surmounted in English.