vim -o a* to open 25 files (filenames starting with 'a') together and search & replace (
:windo %s/old/new/gcI) some common word in these files. Later I found that not all of them have been modified and it seems to be due to that
vim -o opens only 23 of them. However,
vim -O a* can open all 25 files.
So is there any safe way to make sure every file is opened (and thus modified), hopefully not by counting windows by eyes.