That extra 21x2 minutes hardly seems worth it Jorge. Just a little less noise. Doesn't seem to go any deeper in magnitude. Probably better with 22 x 4 minutes. Same total time.
Since you have clear sky.
Want to do an experiment for me? Compare 1 x 4 minute to 4 x 1 minute stacked. Stretch the stack to equal the same background noise as the single frame. The theory is that 1 x 4 minute is better than 4 x 1 minute.