It's only true if you get buildup, your hair cut/texture change, the weather changes, etc.
If you have *good* products and no weather/hormone/texture/major haircut changes, you should be able to use the same products indefinitely. Of course, styles of what you want your hair to look like may change, too.
Currently, I like the separate ribbons of curl effect from using Jessicurl CCSS
. I may at some point want more tunnel/tube type curls, in which case I'd use a different product. When I want my hair to look more bedhead-ish (like today) I use Gelebration