The first week went pretty well, but after that I am having a hard time keeping focused during the exhale and hold. After the third deep breathing rep I am out to just over 3 minutes. Other than using it as a gauge of breathing technique I don't think going really long is the key.
The cold showers are harsh for a few seconds and I'm good after that. I usually go for about 5 minutes, but wouldn't have a problem going longer, and anticipate doing so. I may even buy some bags of ice and try the ice bath.
In the afternoon I have been doing my old, I guess traditional, form of quiet meditation and that has the same calming and head clearing effect. At the same time I am also having focus problems while doing it. I think that is why I drifted away last year as I was finding it harder to stay focused in my meditation, but when I think about it that is the time to keep working at it.
I'll try to update again, and please feel free to update your experience here for information.