The county legislative authority must conduct a hearing on the petition not less than twenty nor more than forty days from the date of receipt of the petition from the county auditor. The hearing may be completed on the day set for hearing the petition or it may be adjourned from time to time as necessary, but an adjournment may not extend the time for the county legislative authority’s determination pursuant to RCW 68.52.140 more than sixty days from the date of receipt of the petition from the county auditor.