Maverick, I appreciate your book recommendation. I shall buy the book.Sure, theta is not static, it changes relative to other things other then time. For example, theta changes with regards to vol, price and even skew. ALL derivatives has 2nd and 3rd order effects which is EXACTLY why retail traders should not rely on them. A pde is simply a measurement of a variable holding ALL ELSE CONSTANT. That does not exist in the real world. ALL other parts are moving and are not held constant which is why technically you need to understand 2nd and 3rd order effects.
Want a book? Fine, you can pick up a copy of "Dynamic Hedging" by Taleb.
I am familiar with partial differentials. In my previous life, I built MRI scanners. I also understand the basic concepts of dynamic hedging. I read several books on quantitative finance. But I had missed Taleb's. I look forward to reading his work as I enjoyed his other book "fooled by randomness".
Thanks again for the pointer.