HWSW is an Arrow Dynamics design. You know - the company that designed the world's first tubular steel track on Matterhorn? (still operating) Or the first Hypercoaster - Magnum XL-200? (still operating) Or the first 4th dimension coaster, X2? (still operating).
How does your 'old and aged' theory apply?
ToT is one of only two reverse freefall coasters listed on RCDB, but the other - Superman, Escape from Krypton continues to operate, and I think as @Slick has pointed out recently, the fact that SFMM took the opportunity to upgrade the control system when they refurbished the ride in 2010 is probably what keeps it running so well.
Neither of these attractions at Dreamworld, based on their cousins from the same manufacturer, should require this much maintenance. The maintenance issues therefore should not be attributed to age, but rather, poor standards maintained by the park and their unwillingness to upgrade older attractions when the opportunity presents itself, instead preferring to let them run into the ground, whilst building the next spin-and-spew.