As for deshi - Who were truly long-term deshi? I can only think of four - Horikawa, father and son, Sagawa, (Tokimune, of course) and Ueshiba. As best as I have read, the others studied intensely for a block of time, and then were free of him. Only these guys, I think, really experienced decades+ of a relationship with Takeda.
If one is content to be a disciple, things are a lot easier. I think the Horikawas had that humility. They had nothing to chafe at because they could accept their lot. Sagawa, I can only speculate, but he, like Inoue Noriaki of shinei-taido, apparently had such "healthy" egos (excuse me EGOS) that they could, I believe, be resilient. (Hisa, Horikawa(s) for examples.
Let me just append to Ellis' remarks a few relevant facts and glosses:
1) FACT: Takeda was illiterate and Horikawa was his scribe. GLOSS: One could go so far as to say that, with regard to record-keeping and business transactions, Takeda depended on Horikawa like a blind man depends on his cane. I've been in enough companies, organizations, and enterprises to see at first hand that the principal -- even the most irascible principal -- rarely subjects the chief accountant and record-keeper to the levels of abuse that other employees routinely suffer. That makes the texture of the relationship between Kodo and Takeda very different from that of the relationship between Takeda and Ueshiba.
2) APPARENT FACT: Sagawa was independently wealthy. GLOSS: Rich people often tolerate eccentricities in their service providers. Similarly, service providers often tolerate eccentriciites in their wealthy patrons, whose EGOS (and bank accounts) are often quite healthy indeed. Again, that makes the texture of the relationship between Sagawa and Takeda very different from that of the relationship between Takeda and Ueshiba.
3) FACT: The Asahi Shimbun provided corporate backing for Hisa's group. GLOSS: Hisa's relationship with Ueshiba, and later, Takeda, was based on OPM -- Other People's Money. Hisa -- not Ueshiba -- was ultimately the gate that stood between Takeda and the Asahi Shimbun's money. Without Ueshiba's services as a buffer or a cut-out, Takeda had two choices: 1) be nice to Hisa or 2) be broke, but for what Sagawa and Horikawa brought in. The choice he made is obvious.
4) Much has been made of Takeda's connections among judges, police, and military circles, with an attendant suggestion that these connections somehow prove that he was a man of good character. To this, one can only say that for every Thurgood Marshall there's a Clarence Thomas, for every Bill Bratton there's a Bernie Kerik, and for every Eric Shinseki there's a William Boykin. The notion that those connections prove anything about Takeda's character is, in a word, silly.
Random musings, take 'em for what they're worth.