There is only one more episode planned, stated to be an informal one (presumably saying goodbye, mentioning any future plans, &c).
There are two aspects that I'm wondering about.
(1) His history of each specific revolution. He has his bibliographies for each on his website, https://thehistoryofrome.typepad.com/revolutions_podcast/ Of anyone has expertise in one of the revolutions he covered: was he giving the current common version (if one exists), or a view that's a few decades old, or his own notions - and what do you think about his take on them?
(2) He has 12 appendices where he lays or 6 comparative revolutionology, as it were. He does have a "General" section in his bibliography. Even more here, do these appear to be his own thoughts, or a school of thought, or uncontroversial statements, or what? I'm more interested in this case because so much of his per-revolution history was narrative with a lot of easy to check basic facts (there's no debate on whether Robespierre was or was not beheaded on July 28, 1794). He approaches the appendices in the same style, so not mentioning his sources, existing schools of thought, possible variant interpretations, or such,l. So I'm even more dubious about the appendices.
My expertise is in common law and history of taxation in common law so I do have a fairly good acquaintance with the English Civil Wars, Commonwealth England, the Glorious Revolution, etc., and the first season of Revolutions was done pretty damn well for a short podcast series on a very complex series of events. Duncan even cited some primary sources pretty dear to my heart re: a side piece of my scholarly writings that’s been brewing on the sidelines for nearly a decade, which was pretty endearing and neat.
I’m not an expert on e.g. the French Revolution (of 1789) or the Russian revolutions of 1905 and 1917 but as a lay listener who is nevertheless a fan, I really enjoyed them, and he treats the multitudinous political ideologies present in Russia at the turn of the 20th century with more care and precision than I can recall in any media aimed at the general public/history enthusiasts.
Basically, a long-winded way of saying that he’s not perfect—because of course he isn’t, aiming to cover so much ground—but he’s pretty damn good and, above all, eminently entertaining. I’ve not heard the recent appendices but from the first few they seem to be less rigorous but intentionally so with all the disclaimers floating about. Definitely a recommendation for good history podcasting.
EDIT: Most of his interpretations are generally accepted, though there are a few choices he makes that clay be subject to disagreement. I can’t recall a very specific example since it’s been a bit since I listened to the first season, but something like dating the end of the French Revolution (1789) is always arguable but a continuum anyway, so anyone who doesn’t baselessly say something like “1791!” and can support their reasoning is on fairly solid ground. He is pretty good on disclaimers when he’s making such choices if I recall correctly.
I strongly disagree with his assessment in the latest Appendix that Cromwell was the “strong leader” who came to restore peace, order, and good government after the English Civil War. Cromwell‘s whole regime was short, marred with utter constitutional confusion and social failure because he tried to impose his staunch Puritan beliefs even harder than William Laud did with high church’s positions. It was a festering wound which bursted into chaos as soon as he died in 1658.
The real “strongman” that fulfilled that final pacification role was not Cromwell - but King Charles II. Cromwell was a failed interlude. Everyone was so exhausted from his rule and the disorder after his death that even the most roundhead of roundheads welcomed a restauration that granted the King the same powers as Charles I would have had, if he had accepted the Grand Remonstrance. And for all his flaws, Charles II made the settlement work.
Cromwell? It’s as if nothing had happened, and the whole commonwealth was a bad dream. Every act pertaining to the interregum was wiped out, physically and literally ripped out of the Hansard.
Even after Napoleon was defeated, his political and constitutional legacy still lives on today in France. The Napoleon Code is still in use today in France. France is still covered with a corps of préfets being the local reach of the French government.
Comparatively, even to this day in the UK, you’d be hard-pressed to find one single element in their constitutional framework that originate or is a leftover from the Commonwealth era. It has been utterly and completely purged (pun very much intended) as soon as Charles II took over.
There are some previous answers in this sub to your question that you might want to review: example one which itself didn't get a historian's answer, example two with a parallel response about Duncan's other earlier podcast History of Rome from u/OniWeird.