Applescript: Help making it more efficent

Question

This is an Applescipt I cobbled together over the years for a daily process I need to run. It works great, but recently my file count has gotten so large it kills my machine and never completes.  I am running this against a folder that has about 500-3000 files a day. I am very novice at AppleScipt so I am sure there is a better way to write it. I tried to put comments through out to explain what it does.  Any help is greatly appreciated.
with timeout of (10 * 60) seconds
    set theFolder to choose folder
    tell application "Finder" --moves files to one folder
        set theFiles to a reference to every file of (entire contents of folder theFolder)
        move theFiles to theFolder
    end tell
    tell application "Finder" --deletes gram and spell files
        delete (every file of theFolder whose name contains ".gram-spell.failed")
        delete (every file of theFolder whose name contains "gram")
        delete (every file of theFolder whose name contains ".batch")
    end tell
    tell application "Finder" --strips date from file names
        set theFiles to files of theFolder
        repeat with thisFile in theFiles
            set filename to name of thisFile
            set name of thisFile to ((characters 21 thru -1 of filename) as string) --trim first 3
        end repeat
    end tell
    tell application "Finder" --adds prompt name to file name
        set theFiles to files of theFolder
        repeat with thisFile in theFiles
            tell me to read (thisFile as alias)
            set name of thisFile to (last word of paragraph 1 of result) & "_" & name of thisFile
        end repeat
    end tell
    tell application "Finder" --Add txt extension
        set theFiles to files of theFolder
        repeat with thisFile in theFiles
            set name extension of thisFile to "txt"
        end repeat
    end tell
end timeout

Answer 1

Oops… The previous script didn't take into account the case where a file has no name extension at all. Here's an improved version:
with timeout of (10 * 60) seconds
    set theFolder to choose folder
    tell application "Finder"
        move every file of the entire contents of theFolder to theFolder
        delete (every file of theFolder whose name contains ".gram-spell.failed")
        delete (every file of theFolder whose name contains "gram")
        delete (every file of theFolder whose name contains ".batch")
        repeat with thisFile in (get every file of theFolder)
            read (thisFile as alias)
            set theWord to last word of first paragraph of result
            set L to length of (get name extension of thisFile)
            if L = 0 then set L to -1
            get text 3 thru -(L + 2) of (get name of thisFile)
            set theName to theWord & "_" & result & ".txt"
            set name of thisFile to theName
        end repeat
    end tell
end timeout