Ever.

Nature, which governs the whole, will soon change all things which thou seest, and out of their substance will make other things, and again other things from the substance of them, in order that the world may be ever new.  Substance is like a river in continual flow; the energies undergo constant changes and do work in infinite variety. There is hardly anything that stands still or remains still.  Observe constantly that all things take place by change, and accustom thyself to consider that the nature of the universe loves nothing so much as to change the things which are and to make new things like them.

Marcus Aurelius, from Meditations