In my setting there are particle shields that can be extended from a central source given enough power and particles to fuel the shield. This is a world where armor has outpaced weapons (nuclear weapons are a non factor). In essence unlike our world, getting the first shot off is not a guaranteed kill, especially for armored conflicts. Machines of war in general are durable because of shielding in this setting. Meaning that units can retreat and fall back faster compared to how we operate today. It would also mean that the actual physical armor isn't completely destroyed compared to a mission/full kill of today.
How much of an effect would this have on the durations of war (5,10,15,20 etc years),given that to knock out an enemy would require punching through the shield before the enemy retreats. This is also assuming that factions have built their doctrine on ensuring that their casualties are kept to a minimum and are swapping shielded and unshielded units back from the frontline as much as they can. For the sake of argument assume that the time it takes to recharge a shield from absolute zero can range from a couple of days, to weeks. The shielding system can be mounted on structures and much larger machines etc, an adequate amount of particles just have to be fed to it and sustain coverage over such a large area.
This is a world with ETC (electro chemical) guns, railguns, hypersonic weapons etc, basically a little more than near future. A whole slew of other defensive counter measures exist in place as well for the survival onion. The shielding is the last resort. Active defense systems, stealth, advanced camouflage, adversarial camo/camera input, better smokes etc. All designed to make it hard to get close to hitting in the first place.
TLDR: Would particle shielding increase the duration of near future modern war between peer factions on full war footing/economy, if so by how much.
Edit: There is an upper limit on how many particles one can charge at once. There's some heavy sunk cost fallacy past a certain point, for example you can't reliably shield a Nimitz Class carrier completely and expect to shrug off a barrage of anti-ship missiles. The generators themselves are heavy and is a design consideration when building things like tanks or shoving generators in buildings or shielding a PART of a ship.