If you fly aeroflot, earn and burn as quickly as you can via Aeroflot bonus.
Earn rates are fantastic for flexible tickets.
Burn by upgrading or flights to small indonesian islands by Garuda.
SU dont seem to have blackout dates - been upgrading for christmas and easter for years. Just need to book before everyone else.
Haven't really seen a devaluation in years as per chart but soft devas are frequent (can only upgrade Flex tickets but the upgrades isn't refundable...).