Our 86 does the same thing. Has from when we bought it. after 2 weeks forget it starting. I got a Knife Switch that fastens to the battery post and I have left it for 4-5 months and engaged the switch and it starts right off.

Consider buying a $20 battery disconnect switch and installing it on your battery.  With a 35 year old vehicle, you can easily have something cause a drain, and when your battery is so low it won't start the truck, it is getting damaged each time that happens. Badly, actually. With batteries now $150++, getting a $50 jump pack and continuing to let your expensive battery get damaged is not a good solution.  With a battery disconnect, when you park it, you simply disconnect the battery from everything and it should then easily start your truck in several weeks when you return.  I have collector cars and they have these switches.  It's also a passive anti theft, and there are disconnects that have a key lock on them if your truck is in an area thefts occur. 

Hello Helpful Folks,

I have been having no issues in the cabin portion of my camper for a while now.  I have figured out many things over the preceding months.  I appreciate all of your input and teachings.  I wanted to reply here because you all know so much, with a new problem. 

The newish issue, is that when I leave the camper in storage for very long (say 2 weeks) I have to jump the battery to get it started upon my return.  I replaced the battery recently and it still happens.  Here are my new questions:

1) Is there something drawing on the battery that I don't know about when I leave?  Someone suggested removing the fuses from the panel when it is in storage.  Is this necessary?

2) I have been jumping it with cables, which works fine, but I am considering another option. I am considering buying a rechargeable battery type thing.  Like a Jackery, but I want it to air my tires up/ and be solar rechargeable as well as jump my battery.  Any suggestions?  It needs to be small as I don't have room for much, unless I want to uninstall my generator (which is broken currently).