People are steadily extending their careers and working longer. According to research by The Motley Fool, today's average retirement age is 62, up from 59 in 2002. People also expect to work longer than before, with the average expected retirement age rising from 63 in 2002 to 66 today.

Why aren't most people working as long as they expect? Unfortunately, it could be due to health or other uncontrollable factors. The same research shows that retirement duration peaked for U.S. men in 2012 and U.S. women in 2005.

The bottom line? People work longer out of financial necessity, putting them in difficult situations as they age. The median retirement savings for Americans between 65 and 74 is only $200,000, which would be just $8,000 in annual withdrawals using the 4% rule.

Investing is crucial for a comfortable retirement, let alone covering your living expenses. Few people are financial or investment experts. But if you keep things simple, you can still find high-quality investments to help grow your nest egg as part of a diversified portfolio.

Here are one dependable exchange-traded fund (ETF) and two blue chip dividend stocks with simple business models and durable growth prospects to help make your retirement more comfortable when the time comes.

Keep things simple with the Vanguard S&P 500 ETF

An ETF like the Vanguard S&P 500 ETF (VOO -0.15%) is perfect for those who want to manage their investments with minimal time and effort. An ETF is a basket of stocks that trades as one. This ETF tracks the S&P 500, arguably the world's most famous U.S. stock market index. When people talk about the stock market, they often refer to the S&P 500, even if they don't realize it.

The S&P 500 is an index of 500 prominent U.S. companies. They must meet specific criteria for inclusion in the index, which helps maintain its quality. While all investments carry some risk, the S&P 500 has proven dependable. Since 1950, the S&P 500 index has appreciated over 35,000%, not including dividends!

^SPX Chart

^SPX data by YCharts.

It's not always a smooth ride, though. The S&P 500 has crashed  in the past as the U.S. economy went through the occasional recession or crisis. Yet, it has always recovered and remains within a few percent of all-time highs today. You can't count on history to guarantee the future, but it's hard to see the train coming off the tracks as long as the U.S. remains a global economic superpower.

Do you want to be more involved in your portfolio? Invest in these individual stocks and sleep well at night

1. Coca-Cola

Every individual stock has at least some risk because it represents a single company, and you never know what could happen. That said, The Coca-Cola Company (KO 0.78%) comes about as close as possible to a stock you can buy and hold, and enjoy decades of sound sleep at night. The global beverage giant is known for its namesake soda brand, but it sells over 200 brands of soda, water, juice, tea, coffee, and other drinks in over 200 countries worldwide.

The company has a seemingly endless growth runway because the ready-to-drink beverage market is large and fragmented. Coca-Cola chugs along due to a mix of population growth, increased reach in developed and emerging markets, expansion into new categories and brands, acquisitions, and price increases, all driving steady revenue and earnings growth.

Coca-Cola shares its profits with investors via dividends, continuously paying shareholders more each year. The stock is a Dividend King with 62 years of consecutive raises (and counting). The stock won't make you rich overnight, but the methodical business and dividend growth can compound over decades. It's one of the few companies anyone can consider for their retirement savings, whether they're young or approaching retirement age.

2. Procter & Gamble

If you like Coca-Cola, you'll probably also like Procter & Gamble (PG 0.53%). As another Dividend King with success measured in decades, Procter & Gamble sells various household products, such as soap, detergent, toothpaste, diapers, shampoo, and personal hygiene products, under a stable of 65 well-known brands. Anyone can use these products. Plus, you generally need them regardless of how the economy is doing.

Procter & Gamble's brands perform well in developed countries like the United States. I also like their growth potential in emerging markets as disposable income rises in Latin America and Asia over the coming decades. These regions each represent a minor percentage of Procter & Gamble's current sales.

The company has paid and raised its dividend for 68 consecutive years, one of the longest streaks of any public company. Procter & Gamble is another slow and steady grower that can prove lucrative if you hold it and reinvest the dividend for two or three decades. That investing philosophy aligns perfectly with someone saving for retirement.