Shrinking mp3 podcasts

I am listening to podcasts mostly on my ancient MP3 player, which has a memory limited to 4GB. I just looked at the last batch copy, it contained about 90 files. I really don't need human speech to be encoded at a bit rate of 128 kbps with a sample rate of 44.1 kHz. It's perfectly audible at 32 kbps and 22.05 kHz, mono, and it takes up about a third of the space. Here is the ffmpeg command that will recode all MP3 files in a folder:

for file in *.mp3; do ffmpeg -i "$file" -b:a 32k -ar 22.05k -ac 1 "../recoded/$file"; done