One can add to income equities on a regular basis, perhaps every 3-6 months, each time seeking the best risk-adjusted value. Even among top-notch companies there are almost always some temporarily in the doghouse whose dividend percentages (of the cost basis) benefit as a result. My current favorites of this sort are Total, ADR (TOT) and Verizon Communications (VZ).
Since even fairly mature, conservative, large-cap stocks tend to go up in value and price over time, whereas bonds typically do not, there are excess profit advantages to owning income stocks over bonds. These extra profits, in turn, are frequently passed along to shareholders via increases in the dividend amounts. Thus a 4% dividend yield at the time of a stock's purchase can become in ten or fifteen years a 6% or even an 8% yield, in relation to the original purchase price (the yield-on-cost). On occasion, the effects of these increases are stunning. CocaCola (KO) paid a 3% dividend in 1988, the year Warren Buffett bought a large number of shares for Berkshire Hathaway. Because of the company's profitability, subsequent increases in the asset's return to shareholders, and stock splits or buybacks that have improved the value of each remaining share, the yield-on-cost of his original purchases is now over 50%.