Time Out
I use a 10 Second time out with a retry. It works ok for me.
Sheet size
I have used it with 80,000 cells at a time. It works fine, I have not seen the retry fail. I am using CellFeed, not ListFeed.
Yes, it does not like large sheets, small sheets of 1000 cells or so are much faster. Even if I only write to part of the sheet, small sheets are much faster. (Feels like it recalculates whole sheets, as does not look to be down to data volume, but I am not sure)
Exponential backoff
Zig suggests an exponential backoff - would be be interested in numbers - what timeout values and failure rates people get with exponential backoff - also the impact of sheet size.
I suspect start with a 3 Second Time out and double with every retry might work, but have not tested it.