Looking into hts-cash/doit.log file:
"
To update a mirror, just launch httrack without any parameters
The existing cache will be used (and modified)
To have other options, retype all parameters and launch HTTrack
To continue an interrupted mirror, just launch httrack without any parameters
"

Does the above mean that you can  use the efficiency of the update with its
use of cache and change the run options? 
Do you achieve this just by re-launching httrack with all of the options
specified?
Thanks
Krys