I'm fairly certain Mr. Estill is correct. Look at your current lease and look for the words X term of years "or as long thereafter as oil or gas are produced". If you are getting a division order now, it means they found something which they have been producing for months.
Look at the bright side, I would much rather be leased to Newfield than to Chesapeake.
Signing a division order shouldn't affect the sale of your mineral rights. I would still try to determine if the division order was accurate.
Unasked for advise here, I would collect royalty for at least 6 months before I sold, as you are selling all the oil and gas that is in the ground, that will ever be produced. What comes out of one well in 6 months to a year is a very small part and probably wouldn't diminish the value even though it may be significant to you.