Question:
I have been buying unit trusts for a year or so on a monthly basis. They are doing well and increasing in value which means I am buying at higher prices each month. Should I stop buying now and let the existing investment hopefully carry on growing without continuing to purchase at increasingly higher prices?

Answer:
This is a classic case of trying to "time" the market. The secret to successful investing is to carry on investing, in good times and bad. Sometimes you'll buy at the peak, other times at the trough. But this shouldn't concern you too much, as you're looking for long-term growth, not short-term gain.

If you feel your particular unit trust will continue to give you good returns, even if the price is higher, then you should carry on buying. On the other hand, you may feel that you have enough exposure in that sector and it's time to buy something with a different focus, perhaps another unit trust with a different mandate. Your aim should be to build a well-diversified portfolio across all investment classes.

The question you should ask is: Will I be able to sell this investment down the line at a higher price than what I'm currently paying?

When it comes to the stock market, the investor who steadily carries on putting in money will do very well over the long term. Historically, the JSE has given the best returns over a period of twenty or thirty years. Your unit trusts are doing so well precisely because the market is so good right now. Don't hold that against them.