Playing Devil's advocate here: Although the Dhamma is timeless, what if what the commentaries says is true - that it is not longer possible that someone can attain arhantship at this time? Given the enormous good kamma needed to be born in a time where the Buddha is teaching, why would it not be possible for there to be a cutoff point when it is no longer possible to become enlightened? Unless you want to posit that we have the same tendancies and good kamma as those born at the time of the Buddha. /devilsadvocateover.
The fact is no-one can know, unless they try and fail - and even then it is not wasted energy. So personally, I wouldn't worry about it, given that even those who say arhantship is not possible say that anagami is.
"If beings knew, as I know, the results of giving & sharing, they would not eat without having given, nor would the stain of miserliness overcome their minds. Even if it were their last bite, their last mouthful, they would not eat without having shared."