Alter the summoning spells so that by targeting an existing (your) summon, you can increase the duration of said spell.
Say you have a Summon IV out, you can use two more summon IVs to triple the duration, instead of having 3 summon IVs out.
Or you have a Summon V out, and you use 3 summon IVs to increase the duration by a mathematically deprecated amount. maybe by 1/5th? Reduce the duration by the fraction of the spell tier, I guess.
Basically this would let conjurors have a cool and neat thematic summon out longer and give it a bunch of buffs and stuff.
Let lesser planar binding also lengthen a regular summon by some amount of time, for those sorcerers with the ability attached to their summoning token
This is a cool idea