[Blind-sysadmins] Domain laptop boot issue

All of our computers are on a Windows 2012 domain. Most of the laptops reportedly work well out in the field. But a handful of them are reported to have very slow bootup and login processes when not able to find the domain controler. The boot up and login take more than 5 minutes on some ocasions. These are all windows seven professional machines set up on a 2012 domain. Have any of you encountered this issue, and do you have any tips or tricks that helped laptops boot up faster when they can't find the domain controller? My minimum specs are I5 with a minimum of 4 gigs ram.Thanks.