What am I missing by only practicing/studying zen? Is it possible to go all the way to the 'ultimate' solely through introspection?

[-_sometimes]

Is it possible to go all the way to the 'ultimate' solely through brutally honest introspection? 

 

My practice is composed of abandoning knowledge and looking as honestly as possible into what I really 'know'. I don't really see what else I can do, since it seems to me the only thing I can 'do' is nothing at all, including not 'doing' non-doing. In my experience, all 'doing' in attempt to resolve the question of existence/experience/suffering is intellectual, based on the attempt to resolve mental confusion, which in itself is a non-problem.

 

Why should I want to practice internal alchemy, except for a potentially longer life?

[RiverSnake]

Many roads there are....people are different and as a result gravitate towards different systems. If your getting the results you want from the method your applying....then there's no reason to even speculate about other teachings. 

 

Alchemy is it's own approach...obviously you haven't studied it to any great degree. So to answer your question...there is no reason for you to practice Alchemy....unless you feel drawn to do so. Stick to what resonates.