If you don't do the sphere in a certain amount of time, will Valygar complain or even leave? If yes, how long do I have to complete this quest?

I'd rather wait until Chapter 6 (when my party would be complete), but if I can't do it with Imoen, I'll give it a try without her.

TIA.

You can postpone planar sphere to chapter 6. Valygar is a patient guy and will not complain.