It's not really surprising that our perception of time is non-linear. In many of our sensory activities, we tend to perceive constant RATIOS of intensity as constant INTERVALS of intensity. A first magnitude star is approximately 2.5 times as bright as a second magnitude star. The brightest stars we see appear about a five times brighter than the faintest, actually, they are about a hundred times (2.5**5) brighter. A similar logarithmic or exponential (actually, its a power law, to be mathematically precise) scale rules our perception of sound.

This is a very useful characteristic for a detector which must function over an enormous range of stimuli; we can function by starlight, see pretty well in moonlight and clearly in sunlight, but the latter is millions of times brighter than the first. Although many mechanical detectors are more sensitive than human biological sensors, none, as far as I know, even comes close to operating efficiently over such a wide range of intensities.

I believe we experience time in much the same way, as ratios rather than intervals. For a five year old, a Christmas six months away is forever in the far distant future, one tenth of his life. For his half-century old grandfather, its only one percent of his life; practically the day after tomorrow.

However, I also believe this subjective effect is variable depending on the time resolution being considered, and the perspective. A boring day seems to last forever, a boring year may, in retrospect, be over in a flash.

If I knew I had a very good chance of living several thousand years, a space voyage of decades or even a century would be well worth it.