You work a week of long hours and want to catch up on your sleep on the weekend. Or you had a crisis and had to stay up most of the night. Or you had to get that paper done for class or that presentation for your boss and "burned the candle at both ends" for a few days to get it done. Now you want to allow yourself some catch-up sleep.
What’s wrong with that idea? It presupposes sleep is like a bank account, and that if you run short for a while you need to get back what you lost when your schedule permits. And that is not the way sleep patterns work.
You really don’t catch up on all your last sleep. You catch up on some of it and eventually get back to feeling normal. Let’s suppose you normally sleep 7 hours per night but one night stay up all night for some reason. The next day you go about your business feeling miserable and being less productive than normal. You also have physical effects of sleep deprivation. Now the following night comes and you allow yourself to sleep as long as you need. How much will your sleep that second night be? 14 hours? No, more like 10 hours.
You typically recover all your lost deep sleep and about half to three quarters of your lost REM sleep. You will not recover much of your lost light sleep.
The record for staying awake the longest sort of belongs to Randy Gardner who set it at age 17 in 1965. He stayed up for 11 days with no sleep while being watched by researchers. We say “sort of” because there are reports of people staying up even longer, either in extraordinary situations or in scientific investigations not as well documented as the one Randy Gardner was in. It really doesn’t matter who has stayed awake the longest; the limit of human wakefulness is about 10 days. And then what? Then the person goes to sleep and sleeps longer than normal. But he or she doesn’t sleep all the extra time lost from Randy Gardner slept about 15 hours after his marathon session and then the next night slept about 11 hours. And that was the extent of his catch-up sleep.
Now people might want to sleep more when they are off work. Sleep is a fun and pleasurable activity and people may choose it as a recreational activity. But that is a different thing from saying they “need” so much catch-up sleep. A normal person who works long hours during the week and runs short of sleep – when Saturday comes that person needs maybe 4 extra hours of sleep to get back to optimal condition. Probably less. He or she doesn’t need to sleep the weekend away.