But the Maitreyas return takes place when human lifespans increase to half a millennium and reduce, etc etc. Have you read the scripture?
I am aware of the Five Disappearances which is attributed to Buddha totalling about 2,500 years after His passing, when Maitreya is to have appeared. Initially He was asked how long His Dispensation would last and He replied 5,000 years but because women entered the samgha, that time would be halved. (2,500)
Thereupon, the dispensation of The Supreme Buddha being now five thousand years old, the relics will begin to fail of honor and worship, and will go wherever they can receive honor and worship. But as time goes on they will not receive honor and worship in any place. Then, when the dispensation has disappeared,
After my decease, first will occur the five disappearances. And what are the five disappearances ? The disappearance of the attainments, the disappearance of the method, the disappearance of learning, the disappearance of the symbols, the disappearance of the relics. These are the five disappearances that are to occur.
If, Ananda, women had not retired from household life to the houseless one, under the Doctrine and Discipline announced by The Tathagata, religion, Ananda, would long endure ; a thousand years would the Good Doctrine abide. But since, Ananda, women have now retired from household life to the houseless one, under the Doctrine and Discipline announced by The Tathagata, not long, Ananda, will religion endure ; but five hundred years, Ananda, will the Good Doctrine abide.
Henry Clarke Warren. (2005). Buddhism in translations. Cosimo Classics, Cop.
(So the five disappearances of 1,000 years each, now, because women entered the samgha, has been reduced to 500 years each period.)