Thanks for the suggestion. I just checked out this site:
http://www.flashlightreviews.com/reviews/maglite_mag-led.htm
This shows the Mag 4D LED at 50% runtime at 43 hours! Holy smokes. That is unheard of in a Mag. One of my biggest complaints has been the ultra-short runtime that I get out of the 4D. I am going to see if I can find the LED conversion for it and if it works like this guy says it does, it might just become my truck light again.
If you go over to Warrifles.com and do a search in the equipment thread, myself and another member reviewed the LED upgrades. I seem to remember he left his on for many days and I used mine 2-hours a night for a couple of months without changing batteries...It really is worth it and puts out some nice light for the dough..Just stay away from Nite Eyez - they suck - get the genuine MagLite LED upgrade and be sure to buy the model appropriate for the number of batteries on deck, (in your case 4)...