Well, 2010 is always a good conversation topic, I suppose....But for me, I don't think one can be speak so certainly of what is the "mistake that cost him the OGM" (if any). Sorry, but it seems that since Vancouver, I've seen people (fans and haters and others in between) in various places argue along the lines of (1) "if he'd only done XYZ, he would have won" (e. g. more transitions, having "better" programs in some general sense (please see below), adding a double after the 4-3, leaving out the quad, etc., just to recall some I've seen), and use it to argue that (2) not doing XYZ is the "mistake" (i. e. the reason he didn't get gold in Vancouver). But in the end, hypothetical statements of type (1) cannot be proven or disproven, nor can they logically be used to prove (2), even if true.
(My apologies. I know maybe this is not quite what you meant, but this type of arguments is maybe something I've become somewhat sensitive to.)
More specifically to Plushenko in 2010, I feel that Aranjuez and Tango Amore had their strengths and weaknesses. Without getting into all that, I just want to mention that it seemed to me that before the 09/10 season started, many people were saying no, it's impossible, he's been gone too long, he's too old/overweight/injured, it's never been achieved before, etc. But after the Olympics, all that was forgotten, and the general chorus, at least to my not-very-objective eyes, seemed to have to turned to why didn't he do this, if he'd
only done that (my italics), this shows he must've not understood modern figure skating/had a bad attitude/been arrogant, etc. To be frank, I find it somewhat ironic, and not in a happy way if I may say so. (Actually, I even want to say that perhaps there might've been something similar in 2006, though he won the gold that time. But that's the topic for another rant.) Overall, I believe that he and his team understood the issues involved. But he's the one who has to skate the programs. Talking about "huge effort to get in shape" and "costing his health"....That's something he's already done, and I would say done more than once.
(More generally, as a side note, may I say that I'm personally not a huge fan of the phrase "good program", as it appears to be often used, in the absense of more detailed descriptions/analysis? IMHO, there are multiple artistic and technical aspects to a skating program, some of which are not necessarily correlated, and some of which may even possibly be conflicting, which the phrase--again just IMHO--seems to have a tendency to conflate. But again....topic for another rant.)
As for what Plushenko needs to do or should do in this upcoming final season....Well, I guess if I were to talk about my own wishes (while making it clear that it is not a matter of what I think he
should do), I hope he skates in a way that can satisfy himself, and that his programs mesh with him physically and artistically. Beyond that, I hope he'll be able to still take artistic risks, and that he'll get good results. But if I have to choose, the first hope is the most primary at this point, for me personally.
Again, I am sorry. A few of the posters here know me from other places, and they know that I have a tendency to get emo/verbose at times when it comes to Plushy. It's one of the perks of being a fan of him, I guess.