Mel took over the reins at the Estadio Benito Villamarin in July 2010 and led Los Verdiblancos into the top flight in his first season in charge.
His current contract expires at the end of next season but is content he can "work with tranquility" - which he acknowledges is a rarity in the trigger-happy La Liga.
Only Real Madrid's Jose Mourinho has been in charge longer - by two months - and the Portuguese's seemingly likely departure this summer would leave Mel out in front.
Seven top-flight teams have changed coaches this season - Deportivo La Coruna on two occasions - after four more departed during the close season. Of that latter group, Abel Resino and Unai Emery have since seen their respective successors at Granada and Valencia sacked during the season.
Mel told realbetisbalompie.es: "When the club had to support me in the past, they did so with a vengeance.
"The club do not have to prove anything. I feel appreciated and valued in the utmost. There is no debate about Betis and me, for better or worse."
Club president Miguel Guillen said in September that he "dreams" of having Mel in charge "for the next 15 years", but Mel said: "I also understand that people get tired of the same faces forever.
"The fact that three years in charge makes you the most established coach shows you the added danger of coaching in Spain.
"My club amply demonstrates that blind trust in me, which is the best scenario. I can work with tranquility. If you add that I feel at home, Betis have it easy with me.
"I will never in my life do anything that harms Betis."