I think you need to take that phrase following "for" as an ellipsis for "as long a time as he could" and the "for" as a standard preposition.  

This follows sentences like:

    He worked for two hours
    he worked for two days

    *He worked for as short as was necessary
    He worked for as short a time as was necessary
    *He worked for as intensely as necessary

    He worked for as long as was necessary
    He worked for as long a time as was necessary

    *He worked for as hard as he could
  
The fact that this does not work with "short" or other adjectives indicates it is exceptional in some way rather than systematic.  

Phil Bralich

-----Original Message-----
>From: "Kathleen M. Ward" <[log in to unmask]>
>Sent: Feb 23, 2006 11:53 AM
>To: [log in to unmask]
>Subject: "work for" plus adverb clause
>
>One of my students asked me what to do with the following sentence:
>
>	He worked for as long as he could.
>
>Now, "as long as he could" is, I think pretty clearly an adverbial 
>phrase, containing in itself a comparative clause with deletions.  The 
>question is, what do you do with the "for"?  I understand that it can 
>be omitted--and then the analysis is easier.  But I would not want to 
>say that an adverbial phrase can be a complement/object of a 
>preposition.  Is "for" a preposition here?  Is it a particle? Do I just 
>throw up my hands and call it an idiom?
>
>How do other people see this?
>
>Kathleen Ward
>UC Davis
>
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