Getting things ready for such a long trip has involved making a list of things we think we would need. We arranged the items, putting them on the bed next to the suitcase and realizing not everything will fit.
Then we were rolling clothes or putting them into packing cubes neatly folded or rolled. Then we put the cubes in the suitcase or arranged the rolled items carefully.
We closed the suitcase and weighed it. Overweight! So we removed some items, re-weigh. Better but wait, something was left out we will need. Then rearranging, repacking and weigh again. Eureka! Just under the weight limit. Now I hope we have things we need. Two months is a long time.