The Prophet (sal Allahu alayhi wa sallam) said about the people of Jannah,“They will be inspired with tasbeeh (saying “subhanAllah”) and takbeer (saying “Allahu Akbar”) as they are inspired with breathing.” (Muslim)
“The analogy of breathing is used because it is something man does with no conscious effort. Their breathing will become tasbeeh, and the reason for this is that their hearts will be illuminated with the knowledge of their Lord, may He be glorified, and filled with love for Him, and whoever loves a thing remembers it frequently.” -Fathul Baari, Ibn Hajar, rahimahullah.
Ibn Taymiyyah rahimahullah stated that this tasbeeh and takbeer will be one of the pleasures enjoyed by the people of Paradise. He said,
“This is not the kind of obligatory work that is done for the sake of a specific reward. It is the same as the kind of deeds that people do for pleasure and enjoyment.” (Majmoo’ al-Fataawa)
Source: “Paradise and Hell” by Shaykh Umar Al-Ashqar, hafidhahullah, pg 304.