Change comes to all things. All things eventually must either grow or wither away. Sunny days give way to cloudy days give way to sunny days. Children come and children go. Glaciers come and go.
Mountains rise and erode away.
The sun shines but eventually will burn out. The universe expands and will either contract once again or expand into insignificance as its density dilutes itself into infinite nonexistence. All things change. The concept of us being servants of God is not the exception. It is an idea and is not exempt from the laws of nature, the laws of perpetual change.