First thing's first...welcome to the Orchid Board.
Now, I'd like to challenge you to use more descriptive words that growers will understand clearly.
So, I'll begin with these:
Cymbidiums are SEMITERRESTRIALS
Semiterrestrials have roots that grow in topsoil or leaf litter, not in the actual soil itself.
Cymbidiums have PSEUDOBULBS (PB's).
Pseudobulbs are translated as "false bulbs". They are the bulb-like parts of the plant that is above the surface of the soil. This plant structure allows the orchid to store water and nutrients just in case there's a drought.
The base of the leaves to a Cymbidium wrap around the actual pseudobulb. Cymbidiums have what are called strap leaves (think about belt strap).
There are more terms, but I believe this is sufficient enough to answer this particular issue. If you'd like, there is a glossary on this site you can check out.
But...
1. Pseudobulbs age. The older the pseudobulb is, the more likely it will get wrinkley, shrivel and die.
2. Leaves age. The older the leaf, the more likely it will turn yellow and fall off.
So...let's be a bit more specific about the leaves...
As a young shoot grows, it will keep putting out leaves. When the shoot gets to be a certain age, it will develop a pseudobulb and swell up. As the pseudobulb matures, the older leaves start to die back. Ultimately the mature growth will usually have two or four mature leaves and a pseudobulb. While the growth ages, the top leaves will start to die back leaving a leafless pseudobulb. Then as the pseudobulb ages, it starts getting wrinkley, shrivels and dies (but hopefully after it has produced new shoots).
I hope this makes the life cycle of the plant clearer.