AD455 - the fall of the Roman west?

[Flavivs Aetivs]

Hmm, interesting - but maintained by whom? Surely not by the emperors in Rome or Ravenna?

Actually yeah it was. Drinkwater, "The Alamanni and Rome," 327-329. The evidence says the local Limitanei garrisons from roughly Mainz to Pannonia Prima were intact, the ones in the area of the Rhine and Raetia show evidence of a mix of Roman and Rhine Germanic recruits. Drinkwater even goes as far as to suggest that Aetius was recruiting them for his field army regiments as well. Of course, these were as professional soldiers and not foederati units.

With a bit more luck and without that damning East-West conflict I firmly believe the West could have been held somehow. It took about 60 years to wear it down.

It lasted as long as it did because it had an absolutely exceptionally competent and capable leader, Aetius, but even he could not have saved it had he lived. There was a growing rift between the Gallic and Italic aristocracies (which ended up in Majorian's assassination), serious flaws in Western Economic policy versus the Eastern, among other reasons.

If we assume Africa had never been invaded by the Vandals and the outcome of pretty much everything else was the same, then after Attila's empire collapsed in 454 maybe, just maybe, it could have survived and recovered without a major empire and serious military threat on the Rhine-Danube frontier.