When does one throw in the towel?

My husband and I have been married (on paper) for 4 years (we've lived off/on with each other throughout the years). We've both been married before and never thought we'd end up like this! My husband's a gambler who works a commission-only job, setting his own hours. The only guaranteed paycheck per month is from my employment. He doesn't mind borrowing $ from his parents, credit cards, etc., so that he can gamble. He even went behind my back and signed up for a "get-rich-quick" scheme that backfired and now we have to pay a monthly fee for 2 years! As you can read, we do not agree on money - nor do we agree on how to deal with his parents, his ex, his son and my relatives. We have gone to marriage counseling twice, each time I have let my husband come home, but each time he refuses to grow up so out the door he goes again. I do care about him, but I don't know that I truly love him anymore because I have been disappointed by his actions so many times. When does one throw in the towel?