Sometimes it seems really amazing to me that energy is conserved exactly. Although it is possible that energy is only conserved approximately but to an incredible degree I think I'm going to go with occam on this one and say that energy must be conserved exactly. Energy is not the only thing though Also rotational and linear momentum and electric charge and baryon number and.... All this stuff remains completely unchanged in time although it wouldn't really surprise me to learn somewhere down the line that baryon number is not really conserved and to a lesser extent I could believe that electric charge might also not be conserved and there are a bunch of other conservation laws that I don't really understand so I should just keep my mouth shut about those particulars.
If you think too long and hard about the conservation of linear momentum you eventually come to the conclusion that it is a consequence of the homogenous nature of space (thank you Emmy Noether) and the conservation of angular momentum is due to the isotropy of space. I often like to think that perhaps our notion of completely closed dimensions within the multiverse is not at all true. In a multiverse it seems to me that the closest dimensions should overlap with one another. There would be no discernible difference between such dimensional neighbors and so there would be no reason for this overlap to cause problems. However I worry sometimes about this world view because it would seem to me that such an overlap between dimensions would suggest a tiny amount of leeway with respect to the conservation laws. Of course the laws would still hold absolutely but it would just be that the conservation would have to be smeared over all universes in order to survive. But such non-conservation events it would seem to me would very probably already have been observed. I don't have a solution though, it is just a troubling challenge for the view I hold of the multiverse.