What to pack???

I can pack for a weekend, or a three week holiday (starting with 21 pairs of underwear) but I have never packed for 6 months.  George and I are reading lots of travelers’ blogs and gleaning  lots of packing tips. Some things are easy to find there and other things  are not so easy.  Flip flops are everywhere but perhaps not size 11 for George. We also have to stock up on our Rx meds which requires a bit of planning.  I normally wait until the last minute to pack, but for this trip, I have started early.