In all honesty, I believe I'm using something like 3ft lines for the tie outs, haha. Last hang I had no experience with tarp lines and only used my hennessy stock tarp that came with lines, so I just sat around camp and made tensioners and lines I would need for that night only. More so to learn how, I planned to get different line soon.
But there's very few situations I can imagine needing more than a few feet of line. Better to have than have not.