Anyone familiar with the internals of the Skywatcher small mounts (SA 2i, AZ Gti, SA GTi), is there a difference in workmanship/ thoughtful design, expected longevity among these mounts?

I see replacement motors are publicly available for the Star adventurer, but not for the AZ GTi or SA GTI. This is a major problem, provided they all come with self-destructing planetary gearboxes in their motor units.
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