His optimism wasn't only at the hopes of finding an adequate replacement. Perhaps that was precisely what his optimism was not. Each new limb was of course an ill fit in comparison. But the ill fit kept the original arm alive, its absent sensors still magically receiving commands and sending back impulses and sensations of all times.
"It's like being married to a ghost" he'd quip. "Or at least having an affair with one."
Instead of replacing the former arm, the new prosthetics provided new forms of experience, new opportunities for thinking about what he could do with his arm. Almost like he was building up in his mind an elaborate plan for some new form of arm, a refashioning of an old concept better suited to the day and age. Tho he never took to building anything at all, only ever thinking and testing out the advent of others. He reveled in having more arms than anyone else, tho different.