I would definitely put farrr more effort into a committed, long term relationship rather than a new fling. After 12 years you know what your relationship with your partner is like and you know that you two can hit it off again -- as long as you talk to and spend time with each other. The man you have been seeing for 10 months? You have not had a taste of what being in a relationship with him is about. He can very well change drastically in a year, two, or 12.

I don't know if you are married, but 12 years is still a huge commitment. Fidelity should come first, IMHO. He has stayed this long with you, he obviously loves and doesn't want to lose you.