Bennet Shale mineral rights

My sisters and I have mineral rights to about 10 acres in the Bennet Shale just outside Ft Worth Texas. A couple years back we were getting checks for $500-$700 each. The checks have since dwindled down to around $100 sometimes less. They will not send a check until it comes to more than $100 so some months we get nothing at all. Ive had a couple offers to buy my rights. Should I sell? Id just as soon wash my hands of the entire thing. From what I understand the natural gas industry will be quite slow fow a long time to come. And if I do sell how do I get the best deal? I know the offers are a small percentage of the genuine worth. Thanks for your time! Ron Johnson