Everlasting Horde Dimension is, between the time speed differential and the fact that humans don't age there, one hell of a resource. Yes, you have to continuously fight an (everlasting, yes) horde of demons, but there are periods of downtime and rest. So, in theory, whenever Batman needs a couple of decades to learn a new skill (and it took him less than that to become the first iteration of Batman from scratch) or think about a problem, he just needs to pop there and work on it in-between fighting monsters (aka physical conditioning).
And that's just cognitive time. If you can find technology that will work there, set up a small base and rotating shifts, fighters protecting a group of logistic support specialists or even researchers, a damn outpost instead of just a person or two... That'd give Batman a terrifying logistical advantage, with computers orders of magnitude faster than anything else, apparently instantaneous technological advances, decades of knowledge and practice every other week.
Bruce has put himself through worse for less of an edge. He'd totally do it. (Granted, Tom King wrote Bruce acknowledging that he could fly, he just doesn't need to, which I'm sure is something he somewhat regrets saying every time somebody cuts his grappling line. In line with Bruce's very precise if awfully impractical line about what technologies he will and will not use — a Bruce that hasn't biotech'd the hell out of himself is, well, he's *canonical*, and maybe even psychologically true, but strategic nonsense — but still, well, impractical.)(As I keep going back to: ultimately, Batman is a drag on Bruce's potential.)
(See also: Ultimate!Reed's Dome, what he did with one, and what couldn't be done with those.)