"I’m confused. I thought the idea of intrinsic value, however it is determined, always includes a time frame, whether 3, 5 or 10 years into the future, so not knowing when you are going to sell kind of makes calculating intrinsic value pointless. Deciding to sell earlier, whether matching, under or over-performing is either good timing or bad luck?

Guessing what the market will do has nothing to do with valuing whether a company’s stock is under or over-priced; going back 10 years or more gives you an idea of the way the stock behaves as a general rule. So, calculating intrinsic value, then adding the margin of safety is supposed to “guarantee” the purchase as a defined investment rather than a speculation."

Theoretically, to work out the Intrinsic Value, you want to figure out how much surplus cash the business will generate across its life time and then apply a discount to give it a value at today's prices. That's usually not possible because it's uncertain how long most businesses will be around for or what the business environment will be like for them, so people take short cuts to figure out a way to put a price on the stock instead.