Charlie Munger famously said “tell me where I’m going to die, so I know to never go there“. While this is clearly impossible, so too is knowing when you’re going to ‘pass over to the other side’. If it were known, retirement planning would in theory be far simpler, since you could calculate exactly how much money would be needed in order to spend a specific amount each day so that on your final day, you spent your last penny.

Of course, it’s possible to estimate life expectancy based on lifestyle, health and various other factors. However, this is only one part of the equation. The other part is made up of just as many other variables that are impossible to accurately predict. Things such as investment returns, inflation and the health of companies from which you receive dividends are all known unknowns. Therefore, retirement isn’t particularly easy from a financial perspective, with there being a real risk that your cash runs out before you kick the bucket.

Play by the rules

As such, it seems sensible to adopt a few simple rules when deciding how much you’ll need to retire, such as investing in shares that pay decent dividends. This is fairly obvious, but even though retirees can have long-term time horizons lasting multiple decades, it still makes sense to buy shares that will allow you to maintain your level of shareholding and spend the income you receive.

As a result, buying shares that pay a 4% yield could be seen as a prudent move. In fact, withdrawing 4% of a portfolio’s value each year has long been held as a retirement ‘rule’ of sorts, with it allowing the retiree to generate an income from their portfolio without sacrificing their capital. And if the companies in which you’re invested pay 4% year in, year out, then your capital can fluctuate as much as it likes and it will still be able to generate an income for you in the long run.

There’s a catch…

The problem, though, is when that 4% yield falls. In other words, the companies that have paid 4% or more in dividends in prior years decide to cut their dividend payments due to either external or internal challenges. Clearly, it’s possible to research the company’s ability to pay dividends. But as we saw in the credit crunch, even companies that had excellent track records of making shareholder payouts experienced deep financial problems.

In this scenario, withdrawing 4% may be more painful since it can lead to the erosion of capital. However, by diversifying among different companies, sectors, geographies and for more risk-averse investors, different asset classes, it’s possible to generate a more stable and less risky income stream. This should enable you to generate a decent income in the long run without impacting negatively on the capital value of your portfolio.

As for the figure that’s required in order for you to hand in your notice at work for good, unless you know when you’ll die and what real investment returns you’ll achieve, then the figure is at best an estimate and at worst a guess. Far simpler is to take out only what you need each year and invest in a wide range of assets that seem likely to generate a high, growing and stable income for the long run.

With that in mind, the analysts at The Motley Fool have written a free and without obligation guide called 5 Shares You Can Retire On.

The 5 companies in question offer stunning dividend yields, have fantastic long-term potential, and trade at very appealing valuations. As such, they could deliver excellent returns and provide your portfolio with a major boost in 2016 and beyond.

Click here to find out all about them - it's completely free and without obligation to do so.

Peter Stephens has no position in any shares mentioned. The Motley Fool UK owns shares of and has recommended Apple. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.