Ukraine could find itself in a position where she runs out of shells and has to sue for peace at any price.

I don't see this playing out as anything less than catastrophic for the internal politics of the Ukraine.

I've mentioned this in another recent comment so excuse me if I'm sounding a bit one-note here but as I see it there are two broad camps in domestic Ukrainian politics which are relevant here (ignoring the Donbas and Crimea for simplicity's sake) - the average Ukrainian who isn't fully ideologically committed to a total Ukrainian victory, this is the type of person prone to war weariness and just wanting their sons to come home alive/wanting stability to be restored etc., and you have the hardliners who are fully ideologically committed to a total Ukrainian victory and nothing less will suffice, this is the type you see in the Azov Battalion and C14 and Right Sector etc. which also happened to be very well equipped, trained, and battle-hardened as well as commanding a disproportionately large influence over Ukrainian politics.

The average citizen would probably be somewhat disappointed in an outcome where there are territorial concessions made but that would be mixed with relief and a welcoming of stability being restored in the country.

Meanwhile the hardliners are basically positioned to stage a coup and everything points in the direction of them staging a coup or starting a civil war in the western parts of the Ukraine should the government agree to territorial concessions (and possibly even just brokering a ceasefire or a peace accord.) I don't see them fighting and dying on the frontlines like this for years just to have the government say "Okay, we're calling it off and we basically lost. Time to pack it in and go home with your tail between your legs, guys!" and for them to be totally cool with that arrangement. I think that most of them would see the government as traitorous if this were to happen.

The shells may run out but the bullets sure won't.