Is it possible to combine prayers even if not travelling?

The Quran says: *"...When you are secure, offer the prayer duly, because the prayer has been prescribed to the believers as **linked to particular times.**"* (An-Nisa 4:103) And the times are defined also: *“Offer the prayer **from the decline (westwards shift) of the sun** till (the beginning of) the chill of the night, and during the accumulation of red lights of dawn. The accumulation of red lights of dawn is certainly visible.”* (Al-Isra 17:78) “Offer the prayer in **two parts of the daytime** and in the hours of the night that are closer to daytime...” (Hud 11:114) Start of Dhuhr is defined: *from the decline (westwards shift) of the sun* End of Asr is defined: *Offer the prayer in two parts of the daytime*, therefore end of asr is end of daytime. But the line between of those two parts of the daytime (end of dhuhr/beginning of asr) is nowhere cleary defined. The Prophet also combined sometimes those prayers without being on a journey or having fear of anything: Narrated from Ibn Abbas: *“The Messenger of Allah combined Dhuhr and Asr, Maghrib and Isha. There was **no fear, no journey**.”* (Muslim, Prayer of the travelers, 6/59) And there are five furhter ahadith on that: (Muslim, Prayer of the travelers, 6/60, 6/65, 6/66, 6/68) **Is it allowed to combine those prayers without being on a journey or without having any excuse (having fear of something)?**