Welfare and Felt Duration

How should we understand the duration of a pleasant or unpleasant sensation, insofar as its duration modulates how good or bad the experience is overall? Given that we seem able to distinguish between subjective and objective duration and that how well or badly someone's life goes is naturally thought of as something to be assessed from her own perspective, it seems intuitive that it is subjective duration that modulates how good or bad an experience is from the perspective of an individual's welfare. However, I argue that we know of no way to make sense of what subjective duration consists in on which this claim turns out to be plausible. Moreover, some plausible theories of what subjective duration consists in strongly suggest that subjective duration is irrelevant in itself.