5000 years is mostly mentioned and 2500 years as the remaining time of Buddha sasana.
Buddhism and Evolution – Aggañña Sutta (DN 27), #17 refers to 5000 years Buddha sasana.
In this post you said “No progress can be made outside the Buddha Sasana – It must be noted that the time limit for Buddha Sasana of 5000 years or so holds only in this “human world”.”.
Why are Tilakkhana not Included in 37 Factors of Enlightenment?, #2 refers to 5000 years.
The Origin of Matter – Suddhāṭṭhaka, #13…5000 years.