Time limits on claiming child support and other claims?

Hello, I have a friend that has been separated from his partner for 17 years. They were never legally married and were together for 10 years previous to the split. They had a child who is now 20. Throughout the years he has paid for clothing, classes, and other items his daughter has needed and has contributed whenever he was asked to. He has recently paid for a little more than half of her post secondary education to date. The mother now married, is just NOW asking for structured child support and wants back payment of it for the last 17 years. He loves his daughter very much but the daughter's lifestyle has at times been uncontrollable. He wants to continue to help pay for her education and has always stated his intentions to do this. The ex and her husband had been having an affair for 5 years and when his then wife found out about it she divorced him and took him for a major amount of $. My friends ex is now trying to see how much she can get out of this long dead relationship.
My friend is not feeling happy about how he is being represented because he is being told to just answer her accusations and then wait for the next ones and then deal with them, etc. He has been doing this and when he replies with proof or a paper trail she renegs on what she has said and tries new accusations which he then answers to. He is becoming very stressed out and does seem to get very much advise from his rep.
Is there not some sort of time frame that one is allowed to claim things such as child support? She had even asked for his house at one point. After 17 years of being apart can this still be done?
My friend wants this whole thing to end and be done with and is willing to be fair but does not seem to be getting any real constructive answers.
He has already spent a bundle in lawyer fees and is not really any further ahead than when he started and is now wondering if all this money has been wasted as well. Besides perhaps get a new lawyer, what should he do?

[tbyte]

The laws vary from one State to the next, but frankly I do not understand why this woman's case wasn't dismissed outright.
Has your friend filed a motion for dismissal?
If he is unhappy with his current attorney, then he needs to get another one.