I want to ask you that if a person wants to work 15 hours in a day for making money and experience and obeying the orders of Allaah i.e. Salat so it is permissible for him to do this or not that he is having love of this world so it is not permissible for him to do this. Please tell me that he can or not according to Sharee'ah?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no harm for a person to work long hours even for 15 hours if this does not result in neglecting or abandoning a religious obligation, like performing the prayers, being dutiful to parents or fulfilling the rights of the wife or children and the like. Remember the saying of Salmaan Al-Faarisi : “Your own self has a right on you, and your Lord has a right on you, and your guest has a right on you, and your family [wife and children] has a right on you, so give each one his right.” Thereupon, the Prophet said: "Indeed Salmaan, has spoken the truth." [Al-Bukhari]

It should be noted that working for long hours does not necessarily mean loving this world and being attached to it. A person may work for long hours in order to fulfil his necessary needs and the needs of whoever is under his guardianship, or in order to pay a debt and the like. 

Allaah Knows best.