We’ve heard it time and again. The current bull market is long in the tooth. The bears are about to seize control.

This sentiment is easy to understand, considering this is the second longest bull market in history. There have been 25 since the stock market crash of 1929, and the average duration of those is 31 months. The current U.S. stock market bull is 8.5 years old.

There seems to be a growing consensus amongst some bearish analysts that markets are ‘over valued’ today and could produce ‘lower returns’ in the future; that the markets’ trees are almost bare of ‘low-hanging fruit.’

They will argue that valuations on many risk assets are high by historic standards. In addition, they will point out that the American economic cycle is in a late-cycle environment, as the current period of growth began in early 2009.

But the bulls will stress that valuations on risk assets are such because with interest rates and bond yields low, investors have few alternatives if they are seeking income. They will also flag up that this is not a normal economic cycle. Low unemployment is not feeding through into higher wages, due in part to the large pool of economically inactive people that are not included in unemployment data.

Those with a bullish outlook will also draw on global data to support their perspective on further stock market gains. Last week the MSCI World Index reached a new all-time high. It is up 15.6% in USD, and 14.3% in local currency terms. The S&P 500, FTSE 100, and DAX 30 stock market indices also saw new highs last week, while the Nikkei 225 reached a 21-year high.

No one can accurately predict what will happen on Wall Street and when markets will finally reach the bottom – it could be a week, a month, it could be six months, who knows –especially with many investors still bullish, stock prices could rise further for a time. Yet, of course, sooner or later this bull market will end.

But, thanks to modern economic history we do know one thing: over the longer term, the performance of stock markets is fairly predictable: they go up. Indeed, for this reason, over a longer time horizon, investing in equities is almost universally recognised as one of the best ways people can accumulate wealth. Indeed, this is why savvy investors know that to make money it’s about ‘time in the market, not timing the market.'

Keeping some ‘skin in the game’ is, therefore, essential. But equally important is how you manage this. It comes down to diversification. Diversification of portfolios across sectors, asset classes and regions will ensure investors are best- placed to take full advantage of the present and future opportunities and to mitigate the risks.

Nigel Green is founder and CEO of deVere Group. One of the world’s largest independent financial advisory organizations, de Vere does business in 100 countries and has more than $12 billion under advisement.