I've been using SLI since it came out back with the first 3dfx and Creative Labs cards. I used SLI right up until the 1080 series, and had 1080 SLI across several gaming systems. No more. VR doesn't like SLI much, and honestly, nothing really does, not enough to make it worth it any longer, only a few FPS games and "AAA" titles that really, really put effort into the SLI profiles/drivers and get the support to do so from nVidia, truly make it worth any extra $. I went to 1080ti and Titan XP single card instead, mostly for VR, but not only for that.
If someday SLI becomes more widespread with developers, and nVidia ensures that it actually WORKS well enough to make the bang/$ worth it, I'll start putting 2 or more cards into boxes. Not until then though.