Keep it running if you are going to be adding films regularly i would say, are you using yammm for the first time on your movie collection or after a rebuild?
I have the same problem but after rebuilding my Windows 7 64 bit pc. Was working pretty well before. I rebuilt pc but the movies are kept on a partition that was untouched during the rebuild so i thought just installing YAMMM would get everything back the way it was. I found a lot of movies had lost their description/review so i tested a movie by moving it out of the monitored folder, deleting the jpg and xml file and then moving back into the monitored folder, nothing updated.
I've reinstalled YAMMM and i have the same setting as the OP and it still seems hit and miss.
Last night i took out all 250 movies from the monitored folder and deleted the jgp/xml for about 10 movies and moved them back in, yammm kicked in and rebuilt the jpg/xml for most of them. Some weren't rebuilt despite having the folder named correctly (as yammm had done on last build) so i had folders called eg 'The Movie (2011)' - i took off the (2011) and yammm kicked in again renaming it with the 2011 and repopulating the jpg/xml. Tried moving more movies back into the folder (without jpg/xml) and some didn't auto populate, removed the year on some and some did, others didn't so had to put in the imdb tt code, some aren't finding jpg/xml whatever i do.
I can see in task manager processes when yammmexe is doing something but it seems to go back to 00 cpu useage quickly without updating movie folders that should be monitored, bit puzzled