3D graphics is something that one has to work a bit hard to learn. To me is not that is difficult, it is just that it has steep learning curve and that it took some time to learn something about it.
Now, if one really tries and practice and practice enough there comes a point when one has learned enough not to forget. After a while is a bit like learning how to ride a bike, once you learn it...
Maybe one day yo will pick it up again. If you start with a different application it may take some time to get readjusted to it. If you have really learned enough about the subject in reality it is far easier o learn a second application than to start from scratch altogether cause many of the principles that apply to one program can be applied to another.
I mean for example in rendering I realized how much more I have learned about the subject of light alone and reflections and refraction and global illumination and a helluva lot of things that I didn't know before or that I didn't know as well.
In 3D modeling even if programs have advanced a lot we still find ourselves having to deal with the most fundamental polygon in the universe which is the triangle and as much as I have learned about modern 3D I still have to go into triangle management all the time and dealing with quads (double triangle faces) which is very common.
So the thing is that once you learn these fundamentals well enough learning a new application is a matter of learning where the commands and functions are located because most of the serious 3D programs out there share many common tools and procedures, enough to make it easier to adapt to another program.
Some people prefer to stick with a single 3D program no matter what but I tell you that I could learn any relatively fast. I mean I have used Ray Dream Designer a bit, Strata 3D a bit, 3D Studio Max, GMax and then I moved to Blender just because it was capable enough and it didn't cost a penny. And I have used a few others too like Sketchup and others. And I have used quite a few different renderers along the line too.
Once you learn enough it is relatively easy to move to a different 3D program or learn a different renderer. The same principles of geometry and light generally govern all those programs and renderers, yes they do have many differences but one learns them and adapt to them.
It just takes some practice and one has to take it one step at a time and be patient, that's all. Now, once you learn it can become quite addictive, it is a lot of fun.
