Hilleberg tents are worth every penny of it and will serve you year round. We went tunnel and have had no issues.
Exped mat - I will second.
As for whether you take a laptop/netbook it is entirely up to you. We took a small 13inch laptop which was invaluable to us for keeping in contact with family (Skype) and updating our journal.
Belarus you will need a visa for... there are details on my journal (signature) on a page called Visas... it is expensive, very expensive to get a visa for Belarus.
Have a look at
Voltaic Systems solar battery chargers. We are looking at getting on in the new year. Still haven't decided on 9W or 6W but I have seen them in action on other tourers this year and have heard nothing but good reports about them. We also have the SON28 hub and use it for USM charging with varied success... didn't go down the e-werks route. I prefer solar which works even in cloudy conditions.
Long tour and I mean long, multi month tours you should consider 4 panniers especially in less commonly travelled areas. You will find you need different kit and suddenly those tiny tubes of toothpaste, small bottles of shampoo and single sachets of washing powder are no longer economical. Neither of the smallest jars of coffee (just tip the coffee powder into a plastic bag to save the glass jar weight)... you will need to carry additional kit and not rely on finding a bike shop - so spare spokes, spoke key, eccentric bottom bracket tool, rohloff sprocket removal tool etc will all need to be carried. You will also need to consider sewing kits, repair kits for things like panniers getting holes, tent getting damaged accidentally, clothes getting very holely, waterproofs getting damaged etc.
We travelled using solely paper maps - most of them picked up free of charge... but that is a personal choice.