Agreed, as with any render "In any software package", the more detailed you make the recipe, the longer it takes to cook.

• Mats/shaders
• Reflection
• Volumetrics
• Lighting
• Polycount

Taking all of these into consideration with each project, you can teach yourself where you want cut corners to accomplish desired results.
Also remember that the end all project can be created in individual parts and assembled in a 2D editor with layers. On the same note, many effects can be created in a 2D postwork enviroment with much more control.

Example: You want to create a lightning or laser effect in a scene. You can place lights close to the ambient effected subjects in the scene with out the actual bolt or beam, then add these elements in postwork. This saves a lot of render time.

All in all, the most important factor in any creation is knowing your tools. Once you logged many hours of practice, your experience will shorten each task. Finally take into account there is usually someone out there that's already done something similar to what you're trying to accomplish. Take full advantage of this and induldge in every tutorial, written, stills & video.
There's tons of stuff out there.

If you can Envision it, You CAN create it!!

p.s.
Light domes can create fantastic real-light effect & shadow. Experimenting with these in scenes with objects with no/or base materials can give you a lot of insight of what your software & hardware is able to produce in a reasonable time.

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Ockham's razor- It's that simple