Let's examine my head then. Since you're invoking history, why don't we talk about that time America fought a war to expel the English king and England retaliated by burning the White House? Where's that fit in?
Exactly! US and UK were enemies, and now they are best friends. Things can change. The geopolitical situation is ever changing and is never static. Isn't that his point? One day, Soviet Union and China are best-buddies, another day, they almost to go nuclear war against each other. Who is to say if China got too powerful, Russia feels slighted, and seek a reset with West? There is a non-zero chance, but should be taken seriously.
How long is "for now"? Because I see "for now" lasting as long as the West exists.
"For now" until China becomes too powerful and US/EU offers a "Reverse Nixon" reset with post-Putin successor. Russia doesn't even need to explicitly counter China, it just needs to flood the 3rd world with 5th gen Checkmates to neutralize China's dominance in the subcontinent or SCS.
There is little ideological, cultural, language underpinning the Russia-China alignment, so if China becomes too powerful, a "Reverse Nixon" can certainly happen. It's a low chance, but certainly China needs to be prepared to prevent that from happening.
How long a time would it take for circumstances to inevitably change?
Oh the flip side, it's not guaranteed that China will stay powerful forever. If China becomes too weak, who knows, Russia might explore some adventurism against China. They say every 200-300 years, Chinese dynasties collapse or weaken. Even the "Century of Humiliation" is not technically over until Taiwan is reunified.
Finally, how many divisions does Russia have deployed against China today vs. NATO?
I think the fact that China is reluctant to formalize a treaty alliance with Russia speaks to the past transgressions (Qing-era unequal treaties, Sino-Soviet split) that cannot be simply ignored by saying: "China will never become weak again" or "We are friends forever", because there is no permanent friends, only permanent interests.
I think you just admire Putin's strongman complex, which is fine. I'm personally against a formal treaty alliance with Russia, but 'alignment' is fine. China doesn't want to be sucked into Eastern Europe clusterfck or drag China into any nuclear WW3 by virtue of a treaty alliance.