I agree, crossing the ocean is different, but once out of the Baltic it's mostly NATO-controlled shores, all the way to Kola bases. http://www.infoplease.com/images/mnorway.gifYou can not measure accurate steaming distances from a World Map. Transit distances for sea voyages are taken from Nautical Charts.
A transit across the Atlantic Ocean is different than a coastal transit where a ship can typically remain half a day steaming from land/anchorage.
I do not understand how you can state they are confident for a trouble free transit if they are bringing a tug.
The crew should not have any problem in the tropic environment if their ships are properly air conditioned, however, electronics (radars, combat systems, communications, etc) require adequate cooling or they get fried.
Sea water injection temperature in the tropics is warmer and will cause less efficiency in the propulsion and auxiliaries steam condensers as well as air conditioning.
That's why they built Whitesea-Balt canal - and used barges to move subs through it, as it's too shallow.
It was mentioned here that the USN also has tugs prepositioned just in case- does it mean their lack of confidence or just common sense?
I remember that the export Kilo SSKs had to be modified for warm/hot conditions- we will soon find out how Kirov class performs (in peace time) in the tropics! There were also Russian lang. reports that some Pac.Feet units will also go to Venezuela, along with SSN/SSBNs.