Neither does mine.. trust me...
Mine is over 23,000$ behind. If he were to show up at my door on a Friday night asking for visitation... LEGALLY I would have to let him have it(since this IS a legal site I won't tell you what I'd really do

) but you can't tell my mom that.
Now, here's another question for you. How is he supposed to pay child support? Is it through the CSE department? Different states and even counties sometimes have different rules. The county I LIVE in puts someone in jail when they are 5,000$ on work release(too bad my court order isn't here). I agree that your ex is far behind but there are questions you need to ask yourself. Can you live without it at the moment? Do the two of you get along? Do you trust that if he wins this lawsuit that he would make an effort to get caught up? Do you think he's giving it an effort to find a job? I know in my county we have the second highest unemployment rate in the state and jobs just aren't out there.
I do commend him for keeping contact with his children... many wouldn't. I'm not saying roll over and take it from him but again we all hit bumps in the road from time to time. If you really think he's making an effort the I would give it some time as long as you can make it. If the two of you can sit and talk about it that would be great. Then make YOUR decision from there. Your mom isn't the one involved in this... You're the one who has to deal with the stress and what not of it all so it's your decision.