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.