We can summon him again and not must to wait until it dies.
Anyway almost all sorcerer skill can use cancel animation technique to make the summon come more faster.
Example: Salamion summon consist of 2 animation: red book appear in front of us and then the character will stick the wand to the ground. So, when 1st animation come out or red book appear, you must move immediately by pressing arrow key, after that the animation will be cancelled and salamion will appear with no delay.
We can also use that technique in summon familiar skill, so when first animation appear, just press arrow key to move, and then animation will be cancelled, but the skill will still come out.
If you get used to this technique, you can use all sorcerer skill while walking with no stop or delay. Just imagine in pvp, when swordsmen / archer chase after you, you can use summon familiar skill while still running, it will be OP hahaha