There actually is a method provided for justice removal, it just takes Congress, which also features corruption unfortunately. Also, just because there is some corruption evident does not mean it is not being prevented at all. Are all 9 corrupt? That would eventually happen if it was not prevented at all.
Importantly though, short term limits would also not prevent corruption, and would probably increase it, as Justices would become much more interested in joining businesses and lobbying organizations after their tenures are up. Hence, a middle ground is probably smarter.