Steadfast Summoner (5e Feat)
From D&D Wiki
Creatures you create are more durable and last longer than normal.
Creatures you conjure, summon, animate, call, bind, craft, or otherwise create gain extra hit points per hit die equal to your spellcasting modifier. If the effect by which such creatures exist has a duration, that duration is doubled.
Your spellcasting modifier increases by 1.