Perhaps the illusion of time accelerating as one grows older is caused by a decrease in the number of hallmark experiences in one's lives. Friends go to high school, go to college, graduate, get jobs, have babies etc. Once you've been around the block a few times, things lose their uniqueness.
It seems time is recalled in terms of emotion filled events. Once the beginner's experience is gone, the encores are perhaps thought less about. Oh, another friend had a baby, Joe got another job, these people got married again, another person graduated from high school, Samantha got fired, my house burned down, (omitted for content) , Jasmine made the honor roll...
So, it seems that if one wants life to slow down, then a change of experiences and habits might work. Learning something new, spending a day at the beach, and changing your lifestyle may produce an overwhelming number of memories so that yesterday seems like forever.
I remember life in blocks of time. At this stage of life I was doing this, and then at this stage of life I was doing this, and so forth. A longer period of time may seem like a shorter period of time (and vice versa) due to the number of memorable experiences. In the short times I wasn't always more or less busy, I just had more things "new" going on.