When an application closes a file, it is left in the cache. The timeout and number is controlled at:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanWorkstation\Parameters

CacheFileTimeout is a type REG_DWORD with a data value range of 0x0 - 0xFFFFFFFF seconds. The default is 0xA (10 seconds).

The value name determines how long a file will remain in the cache after is is closed.

DormantFileLimit is a type REG_DWORD with a range of 0x0 - 0xFFFFFFFF files. The default is 45 files.