If the area of galaxies are to increase with time, but the total amount of energy in the universe
is to remain constant, then the galaxies must change shape with time as well. One possibility is
that galaxies would have a larger disk, but have less thickness. a galaxy would start out as a
spherical cloud, like the Oort Cloud, gradually changing into a disk, getting thinner and thinner
whilst increasing in diameter. Ultimately a galaxy may only be as thick as a single solar system,
virtually invisible when viewed on edge, but having a diameter that would span millions of light
years.

But perhaps a galaxy would need a large central mass. So we might have a huge stellar cluster
in the center, with a thin disk surrounding. A very old galaxy might look like Saturn: