There's a very long history of financial sanctions. Apartheid-era South Africa and Rhodesia suffered for years, but somehow got by (and a lot of oil traders got rich). It can't have done them any good, though. The West managed against OPEC in 1973-74, but hardly emerged unscathed. Cuba also got by, but hardly thriving by the standards of the hemisphere where it lies. North Korea gets by, after a fashion, and scrimps together enough surplus resources to mount a nuclear ballistic missile development programme. Iran hasn't obviously been brought to its knees. Most societies only really prosper with a basic level of efficiency in day-to-day commerce, import/export etc. Undue friction eventually wears things down. *Eventually*, however, is to be measured not in months, but in years or even decades.
So what will be the impact of sanctions on Russia? (- imperial Russia, that is: oligarchs will just have to mourn their yachts in private.)
On the one hand, we gather Putin laid in quite substantial foreign currency reserves (and gold?). Russia is probably OK for food, and obviously awash with energy (Germany's perpetual strategic weakness). It seems - and this is truly remarkable, even granted the well-known long-term demographics - they are short of manpower for the fray, drafting in Syrians, Chechens, and the assorted orcs and dregs of the mercenary world: but sanctions don't really affect that kind of import. Equally astounding, it seems they are also short of military supplies; but China can make good, if minded to do so.
Where's the short term pressure-point, then? Or even medium term? The only compelling answer I've read is that Russian manufacturing - such as it is, i.e. not much to write home about** - is wholly dependent on western imports for vital higher-tech components, and will rapidly grind to a halt without them. Where will this bite? (a) They'll need to import more or less everything from China & India eventually; and (b) their efforts to open up more remote oil provinces will be stillborn.
(b) is an interesting one for the long strategic haul. "Upper Volta with rockets" is the traditional insult, but more recently I've heard Russia pithily described as "the oil exporter that ran out of cheap oil". Yes, exporting oil is just as important to Russia as gas - and a lot more flexible when it comes to dodging boycotts and embargos, as those Swiss-based oil traders will helpfully confirm. But, they're coming to the end of the cheaply-produced reserves. The next few decades depend on opening up some much more difficult oil patches, which will be beyond them (and probably China, too) - this is the province of prime US / UK expertise.
(a), however, bites a lot more quickly, and equates to the severing of Russia from the modern world. Do they care? Well, Putin probably has his populace where he wants them: either patriotically onside, or thoroughly suppressed - and with a near-infinite capacity for suffering privations, let it not be forgotten. And there's always the China trade, energy-for-stuff. Surely that's not even remotely satisfactory, for Putin or anyone else in Moscow? But is it sufficiently intolerable to be a deadlock-breaker, via something like a putsch, or a resort by Russia to massive escalation? ++
I really don't know the answer. Never a good idea to place too big a bet on who can hold their breath the longest. But it seems we may be limbering up for a contest of that sort.
** Obviously, there are some areas of remarkable strength: I gather Russia's titanium industry is second to none. But that's just a North Korea phenomenon. Their trucks (for example) are utter crap: as related here before, when the Chinese were first in the market for gas, Russia tried to make them buy a bundled offering, gas + trucks. The Chinese laughed in their faces. Either gas on its own - and deeply discounted, too - or nothing, comrade!
++ Which can surely only mean tactical nukes, which turns out to be the only military thing Russia still has that impresses anyone. PS, I'm willing to bet most of them won't work, either, if it comes to it. But you might only need a couple ...