The original wildcat opened in 1927. It was rebuilt in 1986 by the same guys who built the Beast at Kings Island in 1979, and all of them ran PTC trains. Wildcat was given a Martin and Vleminckx overhaul in the 2016\2017 season, and Beast is still operating today too.
No matter which way you slice it, Wooden coasters have lasted longer than you're allowing for the Bush Beast. It opened in 1985, having been built that same year. Remember this is a hypothetical question that assumes Sunway took care of the park. If Wildcat can last from 1927 to 1986 with only ordinary (not overhauled) maintenance before a rebuild, and if the rebuild by Dinn and Summers (the guys who built the KI Beast) in 1986 lasted until 2016 when M&V (the guys responsible for Leviathan at Sea World) came along to overhaul it, then why couldn't Bush Beast have received similar treatment from RMC? RMC did New Texas Giant in 2011. 1985-2011 is a shorter period than 1986-2016...?