Current world-wide oil production is c. 83 million barrels per day [1]. With the estimated 511 billion barrels, about 2x of Saudi Arabia’s reserves (2005, [2]), that would last for about 15 years.
Perhaps you are right, but why should they do anything different when all the other countries are trying to do exactly the same? The US just unilaterally extended their border in the arctic.
> [Russia] can never have enough of neither [land and those resources].
That's factually incorrect. For example, in 2010 Russia settled border dispute with Norway relinquishing claims on a huge swath of the Arctic ocean full of resources[0].
[1] https://ycharts.com/indicators/world_crude_oil_production
[2] https://www.nationmaster.com/country-info/stats/Energy/Oil/R...