The rate at which people are able to adjust their way of speaking changes over time. Young children are able to adapt and learn very quickly, whilst many adults change only slowly or not at all. This means that a change to a new variant of an element of language tends to be led by adolescent or young adult speakers, while older adults retain the original variant. This effect allows the use of the 'apparent time' approximation to infer the temporal characteristics of language change in progress from studies conducted at a single point in time. Comparisons of such studies with longitudinal studies (repeated sampling at intervals over years or decades) confirm that the apparent time hypothesis is indeed valid in some cases. I will discuss the effects of the inclusion of such speaker aging in a mathematical model - the Utterance Selection model - of language change, in particular on the time taken for a variant to reach dominance (fixation) in a population.