gdal - Does gdal_calc only support 26 input raster files at a time?

In gdal_calc.py, input files are specified with letters A-Z.

Here are two files, input.tif and input2.tif, being averaged into result.tif:

gdal_calc.py -A input.tif -B input2.tif --outfile=result.tif --calc="(A+B)/2"

I have more than 26 files. What can I do about this?

One possibility: keep adding up files, 25 at a time, and then divide the values by the total number of input files. I think my numbers will become too large.

It looks like the source code for gdal_calc.py could be adapted to process as many images as needed, but the script is a mammoth nested looping function called doit(), so that's a bit scary. Should I really be hacking source code, or is there a better way?

My images are all single-band GeoTIFFs, by the way.

EDIT: After posting, I realized this question is somewhat of a duplicate of this rather incoherent one. Fortunately, the other question does have a good answer showing how to average more than 26 images together from the command line. The answer only works for a predetermined number of images, though. It would be nice to have a general solution that supports a theoretically unlimited number of images.