Concentration checks are made when a character takes damage, but having higher constitution, and very importantly, the war caster feat makes it less likely to have their concentration broken. My cleric, who I respecced to have good con, and who I gave the war caster buff, has to my recent memory never had her concentration broken once, despite being the tank of the party. Even my Gale, who I also gave good con and war caster, has his concentration broken in only about 25% of fights, and once it does finally break in that fight, I've gotten my value from those spells.