Hi Naomi,
Here some test results with one table with 2 005 103 records, PRG and table was palced in one folder, before each teste I quit VFP and than restart it again. I tested only SELECT, not insert and update. All tests are runned once.

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Buffering 5 | TableValidate 7 | FLOCK() | Table was opened | Used in SELECT      | Some records | Result
            |                 |         | before SELECT    | WITH (BUFFERING=.t.)| was changed  |(seconds)
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   OFF             OFF            OFF          OFF                  OFF               OFF          64.286
----------------------------------------------------------------------------------------------------------
   OFF             ON             OFF          OFF                  OFF               OFF          45.805
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   OFF             ON             ON           ON                   OFF               OFF          82.250
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   OFF             OFF            ON           ON                   OFF               OFF          45.184
----------------------------------------------------------------------------------------------------------
   ON              OFF            OFF          ON                   OFF               OFF          44.371
----------------------------------------------------------------------------------------------------------
   ON              ON             OFF          ON                   OFF               OFF          41.110
----------------------------------------------------------------------------------------------------------
   ON              ON             ON           ON                   OFF               OFF          54.355
----------------------------------------------------------------------------------------------------------
   OFF             OFF            OFF          OFF                  ON                OFF          48.395
----------------------------------------------------------------------------------------------------------
   OFF             OFF            OFF          ON                   ON                OFF          49.778
----------------------------------------------------------------------------------------------------------
   OFF             ON             OFF          ON                   ON                OFF          71.191
----------------------------------------------------------------------------------------------------------
   OFF             ON             ON           ON                   ON                OFF          41.477
----------------------------------------------------------------------------------------------------------
   ON              OFF            OFF          ON                   ON                ON           51.246
----------------------------------------------------------------------------------------------------------
   ON              ON             OFF          ON                   ON                ON           57.430
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   ON              ON             ON           ON                   ON                ON           63.301
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I know that this is not a proper testing, because it doesn't have all ovvasions, and doesn't run at least twice, but I have no time for more.