Peter Lynch had a pretty interesting talk where he said that on average the stock market has a sizable dip every few 2-3 years, meaning it's lower at the end of that year than it was at the beginning. Generally though, it goes up over time.
Right, up to now the maximum interval where the market didn’t go up to a new all-time-high is about 15 years, but so far it always ended up reaching a new all-time-high in the end.