Cold Steel:
For years adventist sects, including the JWs, have believed that the dead sleep at death and remain non-existent until the resurrection.
This is really just ad hominem. The notion that 'spirits' exist is not 'bolstered' by assigning the 'alternative' view to 'Adventists'. There is no evidence at all that 'spirits' exist, and no known mechanism by which they even could. Belief in 'spirits' arose from primitive people who were basically scared of their own shadows (sometimes literally). The fact that Adventists have one notion in their range of beliefs that is slightly less irrational than some other belief systems (until they ruin it with the bit about 'resurrection') is not particularly relevant.