Since there are so many mods with Conjuration summons, it can be a bit tricky if you're wanting a longer lasting or thrall variant.
So, out of curiosity. Is it possible to make a spell (presumably Target based) to extend the duration/lifespan of a currently active summon?
It doesn't have to be Target based, I just figured it'd be the easiest method for it to work. But I've no expertise in this to really say with confidence.