Memories and the Speed of Time

I am currently reading The Careful Use of Complimentsby Alexander McCall Smith. It is my antidote to reading The Poisonwood Bible, having already devoured Carry On, Jeeves by Wodehouse.

Reading about two thirds of the way through I was taken aback by an exchange over the relative speed of time between the characters Isabel and Jamie.
I have always wondered why life felt like it moved faster after leaving school. One day I was a student, the next day was ten years later. What on earth was this strange phenomenon all about. I had noticed it, but had never sought an answer.
So when I reached chapter thirteen McCall Smith offered an answer to my question.

Here are the passages concerned:

'It's different. When you're doing something you really enjoy, it does pass more quickly. And it's the same if people are rushing around you. Everything seems quicker.'

'Subjective time,' said Isabel. 'When you're ten, a week is an awfully long time. Now...'

'Yes, it's very odd,' said Jamie. 'I had plenty of time when I was at music college in Glasgow, and it passed very slowly. Now a week goes by in minutes.'

'There's a reason for that,' said Isabel. 'It's to do with memories and how many you make. When you're doing things for the first time, you lay down lots of memories. Later on, things become a bit routine...'

'And you don't have anything to remember?' Jamie asked incredulously.

'Well, you do, but because your life is a bit more routine, and there are few things which strike you as unusual, you don't feel that you have to remember quite as much. And so it seems that time has passed more quickly.'

Oddly, I found this concept rather profound. Perhaps it is me feeling my age.