Use one of these - http://fixmykite.com/proddetail.asp?prod=pkssleevekit to put new sleeving on at the desired length, then temporarily secure them by tying a figure-8 knot at the sleeving. Next time you take a kite in for a sewn repair, ask your repair-person to stitch up the lines too.
i just made a short line set out of some old lines. this post was helpful: http://www.nwkite.com/forums/t-11649-0.html . Forgot to add....check out the second page of the post. The original poster was using 800# line. The lines I used weren't as thick, so I used some para-cord sheath on my spliced loop to give the loop some extra "padding" (see pictures).
Well three ways.
1. Buy Q-line tie figure 8 Knots. That way the next time you need to replace a end you have the Q-line to do it
2. Feed line into itself using a tooth threading tool, or fish line, then sew theaded area with Dental floss, takes 5 for each loop.
3. Thead line through sleevin using said threading tools, and then sew lone together, takes 10 to 15 mins per loop, really does not last much longer than #2, looks so so. unless you use a machine.