Spring lines should be slightly longer, approximately the same length as your boat. Unless your boat is unusually heavy or subjected to severe conditions, a bow line, stern line and two spring lines generally suffice. Spring lines keep the boat snugly near the dock by preventing it from moving fore or aft, while allowing for the rise and fall of the tide. Of course, if your permanent slip has outboard pilings as well, you'll need an additional bow and stern line. If you are off the boat much of the time, lines should be longer to allow for high water from storms and tides.
Short lines are a prime cause of damage.
Also, put the eye end of your dock lines around the cleat, bitt, etc. Conversely, if you're a transient and spend most of your time aboard, put the eye around the fitting or piling ashore and adjust from the boat. Chafe is the nemesis of good lines. Although inevitable, it's not uncontrollable. In a permanent docking arrangement, the chafe problem is most chronic.