[johncoltrane]

All these commands take a count:

    10<C-w>

But I tend to keep windows at equal width anyway.

[jlgreco]

I don't count columns, I resize to taste.

I also resize often, particularly when using vimdiff, because I often use smaller screens (either because I am watching other things in tmux panes at the same time, or because I am working on my eeepc).