One of the most popular bits of fantasy advice is to spend as little as possible on closers because the job turns over so frequently. Close behind that piece of advice is to punt saves entireley because the job turns over so frequently that there will always be opportunities to pick-up the new closer from the free agent pool.
I tend to agree, much more strongly in mixed leagues, but agree I do. However, I do not recall any expert who espouses the wisdom of devaluing closers ever recommending to avoid trading for them for the exact same reason- the job turns over so frequently that it isn't worth dealing a JD Drew for Todd Jones or Mariano Rivera for Vladimir Guerrero.
Why does that natural extension get recommended also? The observation about the job turnover remains the same whether one drafts the closer and loses him or acquires him from another team and loses him. Either path leads towards the inevitable loss of a closer, and both paths cost a $20+ player whether drafted or dealt after being drafted.