I tend to place it at the bottom to preserve "history" of the file. But sometimes I slip off my convention because the top of a constructor is sometimes closer to the variable declaration.
Terrible idea!
History should be left for version control systems (you do use a VCS right?). I try to format each commit as if it's a publicly published code.
Why not just tell the compiler to randomize those statements that can go in parallel, or just outright parallelize them.
Lazy evaluation, anyone?