Why Tirumala Sri Venkateswara swamy footwear is eroding?

Whether you observed Tirumala Sri Venkateswaraswamy footwear or not they are big in size. You might also hear they are getting eroded along with time. People and priests believe that Sri Venkateswara swamy has abundant love towards her wife Alamelu Manga Devi. After temple is being closed, lord wears his footwear and get down from seven hills to Alamelu Manga Devi and returns back to his position by the time of suprabhatam.