unmounting wim files takes a very long time - is this normal

Build works okay (although won't boot as per other post) but the stage where it is unmounting wim files takes an absolute age to run - is this correct or is there something I am doing wrong

Have been using winbuilder and win7pese for ages and never noticed this issue in the past

it is correct,
you probably changed your source from w7sp0 to w7sp1,
or you change your w7sp1 source that belongs to higher level of distribution (enterprise  ;) )

in all way,
this slow mount-unmount trouble was created by ms... 

in any way,
there is solution 
Use
\Utils\"Extracted_Wim_Folders"

hence your builds with whatever source will not have any delays 

excellent thanks Lancelot - will give that a try