But she can't age physically, and dies at a point of time.

Technically in a separate timeline where Shirou managed to fuck up Kirei without being fatally wounded she could just anchor her soul to a different vessel while retaining her magic circuits, would also make her superior to most Servants as she would be a top rank Magus with proper physical capabilities and heavy knowledge about Grails, Einzberns, Third Magic, Command Seals, Spiritrons and so on.