Orochimaru initially wants sasuke for his sharingan, so he could learn all ninjutsu, which was his goal right?

But seeing how he transfers to another body, the aging process is still there. That means that eventually sasuke's body will die of age. So with 50+ years in sasuke left, it doesn't seem like it's enough to learn all 'jutsu'.

Afterwards he'd just have to find another body, and then he'd lose the sharingan. Since only 2 uchiha members are left, he'd have to take Itachi or something, but Itachi is older than sasuke as well.

I do acknowledge that in the end he's going to lose in some form anyway.