Common variables for matrix items on many different forms

Are there any known Panorama X performance issues if I use the same variables for all of my matrixobjects which are used on many different forms. Basically I designed one, got it working with the search widget and then copied that to 8 different forms. Only one form is open at a time. Do all MatrixObjects have to do some cpu time to update even though they are not visible?

No, MatrixObjects in closed forms will not take any CPU time at all.