You would think that after nearly a century, the Clanner would at least make EI users live longer so they can fight without going nut when they didn't expire before the mental sickness kicks in
One gaming group I played with came up with an interesting explanation for the fairly strange lack of progress in this area. Obviously, this is fanon, but particularly elegant as an explanation.
The scientist castes of the Homeworld clans
did come up with a therapy to mitigate the effects of EI in the late 3080s after the had a chance to compare and contrast some of the Blakist implants. They learned a lot from the toaster-worshipper tech, and figured out a thereputic regimen that would slow down and even reverse the degenerative effects of EI.
Problem was, the therapy requires several consecutive months of downtime outside of the cockpit of a mech in order for the neuroprotective therapy to work its magic. The tempo of a clan warrior's training regimen is such that this basically never happens. Maintaining proficiency is more important to them than not going insane. So, while they do take the drug cocktails the scientists cooked up to offset the problems, it makes very little difference if they never take a break. The technology does exist, but its limitations clash with clan culture so severely that it rarely helps anyone.
Anyway, that's what we came up with.