“…Structured population models have been studied at least from the sixties [3], and it is still an intensively studied area [1,2,12,13,16,23,29]. One important property of age-structured population models is the so-called asynchronous exponential growth/decay property, i.e., when the age distribution tends to a limit independently of the initial age distribution (see, e.g., [10][11][12][13]15,23,[30][31][32]).…”