Old Texas lease - still valid?

A oil, gas and mineral lease signed by my relatives in 1976 lists the primary term as 10 years and thereafter unless there is a cessation of 90 days. There have certainly been more than 90 days without well activity or payment since I inherited the mineral rights 12 years ago. Is the lease still valid? The lease, of course, has passed through numerous companies and the latest is drilling in the area. We’re trying to determine if a new lease is required. Obviously, the oil company considers the old lease valid. Thanks for the help.

Ask them to validate why the lease is still valid. Did they pay the shut in payments required (if in the lease)? Make them show continuing activity with no 90 day breaks.