Scarlett Johansson is divorcing after just two years. Which confirms my theory that the celebrity year is getting shorter. It used to be the same as the dog year – one human year would equal about seven celebrity ones. So while most of us would be able to squeeze only one or two marriages into the average lifetime, your Elizabeth Taylors could get nearly into double figures. Contemporary stars live their lives at an even more dizzying pace. You've probably had orgasms that lasted longer than some of Britney Spears' marriages.

Celebrity pregnancies are also much shorter than normal ones. We are expected to carry our foetuses for 40 weeks (in France it's 41 weeks, which must be torture given how much they like pate and runny cheese), but celebrities can replicate themselves more quickly. I heard that Jennifer Lopez was expecting while I was paying for a bedside cabinet in Argos. By the time I was called to my collection point, she'd popped out twins.

In turn, these babies leap from the womb with their circadian rhythms set to celeb time. At 13, Lourdes Ciccone has her own clothing range. Suri Cruise is rumoured to be in talks with Gucci to see if she can fit being their creative director around her schedule of pooing and gymboree. And Willow Smith is taking a break from her successful film career to have an international pop hit with "Whip My Hair". She's 10 years old. I'm 37 and the apex of my professional life was appearing in Russ Abbot's Christmas Madhouse.

Given the accelerated pace of their lives, it's no wonder the famous are so concerned about ageing. Heidi Montag has admitted to having Botox at 23, which is fair enough; in human years that's 161. Actually it's probably more, as the laws of celebrity physics state that the reality TV star year is even quicker. Soon there will be in-utero injections for pumping Juvederm into future American Idol contestants.

The no-mucking-about attitude that has allowed these people to excel in their chosen fields naturally leads them to demand fast results in their personal lives. So I've done some calculations, and I reckon we need to count celebrity years in line with mouse years – 1 to 34. That means Scarlett and Ryan Reynolds managed an impressive 68 years of wedded bliss and Justin Bieber is 544 years old. Does that make it any less creepy that I want to marry him? Only for about five human minutes, obviously.