Yes; I like that; I hadn't really thought of VRs, simply because I was thinking of all the things I'd do in, the real. Funnily enough, I started a sci-fi series on Steemit, called; Asimov's Ghost.
In that, we all live on the Q-block (quantum blockchain), and sure enough, most of us, decide to spend most of our time on it.
However, technology also enhances our physical experience, through our nanoswarm and empLinks, giving us thousands of extra senses, and experiences.
I think the biggest problem with a galactic size Matrioshka brain, is the amount of time taken to process between each node. I guess with some kind of quantum tunnelling, that problem might be circumvented. If not, then the speed of light, is glacially slow, over those kinds of distances.
With regards to such large scale structures and the immortal nature of synthetic entities, I don't think they'll see time the way we currently do.
I'll be certain to checkout your Asimov's Ghost series.