Unfortunately, as "data points" go, cephs die for unclear reasons a lot. I think the main point of recommendations that the ceph care folks make is that there seems to be a decreased mortality rate with "good" practices. If you try this, please do report success or failure, but note that it's one data point among many. One reason I respect TONMO's husbandry folks is that they emphasize practices that seem to lead to good pet experiences for both the octo and the owner... this isn't necessarily "the one and only true way" of octopus-keeping, but many other recipes seem to have a high mortality rate. Because we don't encourage pushing the envelope on the parameters, there may be some "folklore" mixed in that isn't really significant, but running tests to check all the possible factors over a significant statistical sample space just seems cruel... it will be interesting to hear if you are successful, but it won't be entirely clear what each factor contributes in the big picture... e.g. how often the stability of a tank cycled less than 3 months is insufficient for the bioload of the octopus isn't really easy to tell from one sample, and whether there is "stuff" in your water supply that RO/DI filtering would eliminate depends on what water you start with, of course. And presumably there are other factors, like how closely you monitor your water chemistry and how often you do water changes, both of which could compensate for cycling and skimming, maybe.
I'll keep my fingers crossed for your octopus in any case, and I'm interested in the outcome, but I think it's important for us to try to present the husbandry suggestions that seem to have a better success rate. I know the "list of octopuses" has lifespans and, when known, causes of death, but I don't think we have full data as to water type, cycle time, skimmer, used vs. new tank, tank size, water volume, temperature, diet, feeding schedule, and so forth, so a lot of the evidence is subjectively observed trends. Maybe we should set up a spreadsheet to try to get better raw data and see which correlations are the biggest, but that's a big project... in the meantime, it seems like trusting the collective experience of TONMO octo-keepers to provide a working "best practices" recipe seems, to me at least, to result in a lot of stories of long-lived and interactive octos.