Most people learn about the Saturn return around age 29 and only later notice that Jupiter has its own return every twelve years. The two cycles run on different clocks, so they rarely line up. When they do, the timing is worth paying attention to.
Saturn takes about 29.5 years to circle the zodiac, so its returns fall near 29, 59, and 88. Jupiter takes about 11.86 years, so its returns fall near 12, 24, 36, 47, 59, 71, and 83. Put those lists next to each other and one age shows up in both: the late fifties.
The late fifties
Around 59, Jupiter's fifth return and Saturn's second return happen within a year or so of each other. Saturn asks what structure you are going to keep for the next three decades. Jupiter asks where you still want room to grow. Getting both questions in the same stretch of time is why many people describe that period as a real turning point, such as retirement plans, a new field, or a move.
Near misses earlier in life
The earlier returns don't overlap exactly, but they bracket each other. The Jupiter return at 24 comes about five years before the first Saturn return, and the one at 36 comes about six years after. Read together, they often show a pattern: a direction chosen around 24, tested around 29, and expanded or abandoned around 36.
How to see the overlap in your chart
Exact dates depend on retrograde passes, so the clean ages above can be off by months. A Jupiter return calculator will give your Jupiter return dates, and you can compare them with your Saturn return dates to see how close the two cycles come for you.
It also helps to check whether natal Jupiter and natal Saturn aspect each other. A close square or opposition at birth means the two returns often bring the tension between growth and limits to the surface.
If you're starting from scratch, Astrology Geeks has free calculators for the natal chart and the return charts.