Yes I agree. Wars should last a little longer, but also peace times should last a little longer too. Most of the time on my playthroughs they declare war again as soon as they declare peace. Most of the time there is no time to regroup and replenish lost troops.
But for that they need to add things to do while at peace. Right now the game is heavily focused on war, so there is nothing to do at peace time other than killing bandits, replenishing troops or tournaments. Hey TaleWorlds, where are them feasts?
And also kingdoms shouldn't declare second wars as easily when they are already at war. Only if they are winning by a landslide. I don't usually cheat, but the console command that I use the most is "campaign.declare_peace" lol. I know they did this to prevent snowballing, but I'm sure there are other ways to prevent it. Like for example, make it harder for AI to take settlements (give defenders buffs during simulations).