All labor performed or materials or services furnished by any person entitled to a lien under the provisions of sections 57-801 to 57-820 upon the same leasehold interest for oil and gas purposes or the same pipeline shall for the purposes of sections 57-801 to 57-820 be considered as having been performed or furnished under a single contract regardless of whether or not the same was performed or furnished at different times or on separate orders. Not more than four months shall however elapse between the date of performance of such labor or the date of furnishing such material or services and the date on which labor is next performed or materials or services are next furnished.