It seems to be quite difficult to pack things for such a long trip in different climate and for different needs. However, after careful selection, we ended up with two backpacks 20 kilos each and a small backpack to carry our laptop and for some stuff easy to grab.
Now, after 4-month trip we are a bit experienced, so for the second part of the trip we definitely take the following stuff:

- 60 and 80 litre back packs
- trekking shoes
- sandals
- 5 t-shirts
- 2 pair of light trousers (one that can be unzipped to shorts)
- underwear
- a pair of trekking socks
- warm sweater
- swimwear
- raincoat and raintrousers
- head lamp
- electric water cooker for tea, coffee or soup
- mug
- tea and coffee
- travel towel (quick dry)
- sun protector
- swim glasses
- pocket knife
- backpack covers (useful for transportation)
- sleeping bag
- wet tissues (for poor hygienic conditions)
- toilet paper
- insect repellent
- first aid kit
- LP guidebooks
- laptop
- mobile phones (if you want to reserve hotels or loose each
  other or to call home); make sure you have one that is sim-lock-
  free so you can put in local prepaid cards
- GPS-device
- all necessary chargers
- business cards (easy when exchanging addresses with people)