RedRabbit:
1minute- does your wife find that she is often at the 400 end of the zoom?
Just a guess, but for a preponderance of her medium scale wildlife shots (birds, rabbits, coyote, etc), I think she's at the limit. Other times though, when she has some luck and gets close, she's complained that the 100 mm end is too much. That's when she starts chopping off antler tips and such. Those are typically not moments where one can be shuffling about switching things out.
In total, she packs around a true macro (don't remember the designation), a 24-70 mm, a 38-135 mm, and the 100-400. Most of the time, it's the 100-400 that's mounted if wildlife is the objective. When she finally retires and has the time, I'll probably spring for a prime 500. That should be grounds for fine Shiloh for me a bit later on.
