I also don't use a ridgeline with my tarp - if the tieouts ever started to weaken, I might consider switching, but right now I don't bother.
The amount of cordage I use varies - the tieouts to the trees are usually about ten feet on each side, and then I have several tarps. My summer tarp has 8 foot lines on each of the 4 corners, and I carry maybe another 10 or 20 feet of spare cordage just in case. My winter tarp has more tieouts, but those tieouts are also more likely to be pitched close to the ground, so I carry a handful of 4-6 foot lines, and a couple lengths of shock cord to pull the doors shut too.
For my hammock hanging, I also use an all-webbing suspension, like C_Kyle. It's much quicker and easier to adjust, and doesn't add a ton of weight. If you DO decide to use rope to hang your hammock, I would strongly suggest still using webbing "tree huggers" to wrap around the tree and tie the rope to. Some people really freak out about you tying hammocks to trees and potentially damaging them, so even if you don't believe you are gonna cause much damage, it's worth putting the webbing on to make the appearance that you're going to some effort to protect the tree. Hammocks are already banned in a number of places, and as they get more and more popular, we should be doing everything we can to keep them from getting banned in more locations.