Everyone has had good suggestions: repotting and trying to put some of it in water so it will grow more roots.
If it's the ivy type, you can make it last a long time by cutting it back and putting the cuttings in water to re-root. I have one that my grandpa gave me when I was about 6 years old. My grandpa died when I was 11, but that plant is still going strong and I'm 27 now. Every 6 months or so, I take cuttings off the vines, stick them in water till they root, then put them back in the pot. That poor plant has been through the worst conditions possible - like in college when I had an apartment with one teeny tiny window and it only got watered every couple weeks.
Now it's looking beautiful. My hubby has a cissus vine that is the same way - his mom bought it on her way out of the hospital when she gave birth to him, and he's almost 30 now. They've always done the same thing with cutting it back, re-rooting, and putting the new ones in the pot. That plant is HUGE now.
So anyway, if it's the ivy type, you might try that to keep it going longer. If it's not the ivy type, I'm not sure what else will help. Good luck!