50 hours should be more than enough. Since LANDesk is already in the environment you probably have your applications packaged already. I spent a couple months packaging everything for us a couple years ago, but that's mainly because a lot of our applications have customized installs and it took a long time to test and get everything to install right. Now that everything is packaged separately I can swap in new or updated versions of applications fairly easily, then just run the gold template again to create the locked copy everyone else uses.
I also update the core image once a year to install all the patches from the previous year. Cuts down on the time it takes for the patching component to run (shaved off 20 minutes a couple weeks ago).