I'm a bit surprised to hear some think networkers only have 11-13 years left. Perhaps the /9s, but those with significant alterations underneath should keep going, particularly as other electric trains have like the 315/17/19? 40ish years planned for them?
The classes you mention that are running, or are planned to run, for longer than 35 years are steel bodyshells and have potential to easily cascade. There is wealth of knowledge and data within the industry on how steel shells age and how to keep them running safely.
465's are aluminium shell and the same level of knowledge and experience and data does not exist; when the BREL 465's shells were discovered with structural corrosion expertise was brought in from the aircraft industry to model and understand the implications.
The 35 year life is based on the predicted fatigue life limit of bodyshells and bogie frames.
As you say, the auxiliary equipment can be kept running with regular overhaul and OEM support.
My personal view is Angel owned GEC built 465/466's will not be life extended beyond 35 years; the traction equipment is obsolete, and has been for some time, and I don't believe Angel have any plans to retraction their units. Some GEC bodyshells have issues with structural defects arising from build and there's the elephant in the room with regards to the liquid sloshing around inside some of the GEC shells and what effect this is having on the life of the shells. Plus there was an issue with some GEC bogie frames and whether they'd require repair or replacement due to manufacturing defects.
The Everhsolt owned BREL built units could be life extended; they've got the Hitachi traction equipment with Hitachi support (although I don't know how long Hitachi signed up to support this), Eversholt have done some work on bodyshells with their past corrosion repair, it's a larger fleet and any work has the potential to read over to the 365's as well.
Like I say, my view and not anything other conjecture....