Using perceptual adaptation for enhancing realism of VR/other entertainment
Adaptation to altered vision is probably most well-investigated using prism-glasses. Prism glasses can shift the visual horizontally, for example by 20 degrees (Redding et al., 2005):



The use of horizontal shifting goggles has been investigated intensively to treat the symptoms of attentional neglect. Neglect occurs due to unilateral parietal brain lesions. For example, a lesion in the right hemisphere may induce left-sided neglect, where the left part of the visual field is seen, but simply not processed and neglected (Rosetti et al., 1998). Wearing prism goggles for approximately 6.5 hours/day, over the course of 2 weeks has been shown to reduce the symptoms of neglect significantly by as long as 17 weeks(!) after treatment (Frasinetti et al., 2002). 

For the treatment of a neurological disorder such as neglect adaptation to prism glasses is great. However, treating healthy controls with comparable methods may induce unwanted side effects. 15 min of prism exposure has been shown to lead to several degrees of error in pointing tasks, for up to two weeks after the adaptation in normally sighted controls (Klapp et al., 1974). 

To mention some studies closer to your question: in a virtual reality experiment subjects wore a head-mounted display that shifted the virtual position of their eyes. Their performance on a hand-eye coordination task first decreased by ~40% and then increased again with ~30% after adapting to the display. After taking the display off, there were transient after-effects, that impacted eye-hand performance (Rolland et al, 1995; Biocca &amp; Rolland, 1998). In other studies wearing a head-mounted display longer lasting discomfort was reported in 5% of the subjects (Cobb et al., 1999) as well as binocular stress after removal of the display (Mark Mon-Williams et al., 1993). 

Although the latter studies did not report serious after-effects, the more rigorously performed studies with the prism glasses have shown long-standing effects after visual adaptation. Hence, although the performance with virtual-reality head-mounted displays and comparable devices will undoubtedly increase after adapting to them, visual functions in everyday life may correspondingly be compromised. 

So although this answer may not be addressing all your practical questions, I would say it is not advisable to let one actively adapt to head-mounted displays, or other wearable virtual-reality glasses that change visual function in the first place.

References
Biocca &amp; Rolland, Presence 1998; 7:262-77
Cobb et al., Presence 1999; 8:169-86
Frasinetti et al., Brain 2002; 125:608-23 
Klapp et al., Perception &amp; psychophysics 1974; 15: 399-400
Redding et al. Neurosci Biobehav Rev 2005; 29:3, 431-44
Rolland et al., IEEE Proceedings of VRAIS 1995
Rosetti et al. Nature 1999; 365:166*9