horowitz near the end was heavily medicated, ruining his performances for several years - i heard a bad concert at Ambassador in Pasadena where he could barely keep it together onstage. Then someone got him off his meds and he played a lot better apparently -
there are lots of things going on in peoples' lives
but overall his technique did *not* suffer after his comeback in the slightest -
horowitz is always a pleasure to me, if sometimes a guilty pleasure - he couldn't play beethoven very convincingly, but man, those 'carmen' variations are just staggering -
his greatest record: the rare double LP 1953 25th anniversary recital at the Met - a strangely bewitching Schubert B flat, the last piece you'd think of with Horowitz .. the eeriest Scriabin black mass ever, Prokofiev's 7th last movement as an encore - then, serenade for the doll
these recordings have not, so far as I know, been reissued on CD