To be fair, imo if a company was so steadfast on the 30 day rule, they would set up the message boards to auto delete inactive threads after 30 days. when I was a forum admin, thats how I had mine set up :p
Failing that, if they wanted an archive for people to read. They could lock them after 30 days of being inactive.
They shouldnt ever delete anything, there is good info out there. But I support auto lock after 30 days of inactivity... that would stop all this pointless necroing