Russia to Portugal

Hi, I'm a cyclist with a little experience of cycle touring (ie the most ive done is about 3000km over five weeks) and now I'm planning something a bit more ambitious. I want to cycle across Eurasia, probably Russia to Portugal.

Could anybody give me any advice, especially
1)Advice on routes
2)Advice on probable distance
3)Advice on seasons when to (not) be where (i was hoping to leave next july, but on reflection leaving halfway through summer seems unwise probably)
4)Advice of anyone who has done anything similar. I tried googling a few things and I found some stories on this forum, but it would be really good to hear from someone who has done a similar route.

I'm planning to do it quite fast probably- one of my friends who i have discussed doing it with and i were thinking 100 miles/165km a day, 6 days a week, for however long it takes.

Obviously this is all in the very early stages of planning, but any info would be really appreciated!

many thanks, will

*echt*