Also try simply "gq" + down arrow or "gq" + up arrow to realign line lengths to the paragraph length in the up or down direction. Or you can do "gqap" to do the whole paragraph regardless or where you are located. This helps me keep pretty 80char paragraphs when writing latex or .rst or .md files, and the separate lines get merged to a single line by the text processor.
edit: To explain better, it basically re-wraps text in the optimal way into a paragraph. So you can not worry about spacing while typing and editing, and then when you are finally done you can just select the text and fix the wrapping really easily.
edit: To explain better, it basically re-wraps text in the optimal way into a paragraph. So you can not worry about spacing while typing and editing, and then when you are finally done you can just select the text and fix the wrapping really easily.