I’m a big believer that knowing your time horizon for investments is very important. Unfortunately, many investors, and definitely the media, live in the short term when in fact your needs are middle to long term.
I read this interesting blog (link below) that really sums things up. The only important thing is the probability of reaching your goals over the time frame specific to you.
A time frame super long (over 100 years) like some stock market charts is really irrelevant, as is a super short time frame, except to the degree it forces us off our personalized investment plan.
Anyway, interested article about time lengths and investing.