Simply split/ duplicate the layer - one with the expression, one without. also consider "baking" the keyframes with teh Convert Expressions to Keyframes keyframe assistant.
What did you mean, when you said "Also consider "baking" the key frames with the convert expressions to keyframes keyframe assistant."?
Baking in motion graphics refers to taking an animation that is done via code and making it keyframes only. That way the code is no longer involved.
If you use the Convert Expressions to Keyframes keyframe assistant, it will take all the animation and make it keyframes instead of live code.