The club is well known for recruiting players based on experience and records. This is a team who still field players who are aged 30 plus so its no surprise to me if they want to sign Di maria at age 34. They believe experience gets the job done so I don't think Juventus wanting to sign Di maria at this current stage of his carrer are worried about getting top performance from him.
Juventus have no plans for the long term. Their goal is to perform well next season. Because their performance last season was completely unstable. And so they want to take Di Maria to the team. Di Maria is a very talented player. Although he is older, but his fitness is good. It looks like he will be able to serve the team well for the next few seasons.