The closer one gets to an Infinite Eternally Expanding Universe the greater the probability of non-existence. If we exist in an infinitely expanding Universe then the probability of our actually being present in a finite defined time surrounded by a measurable space is exactly zero.

And what about time and space? Are they really valid dimensions that can be reliably measured? They seem to shrink and stretch depending on relative motion.

Is the idea of the Eternal Universe having size or shape dependent on the relationship between time and motion?

At the Speed of Light (or more properly The Speed of Causality) time and space change places. Perhaps saying that the Universe is infinite in size is a misnomer. Particles traveling at the speed of causality are standing on the cusp of time and space. To an observer straddling that point the Universe would be perceived as a singularity. Maybe the best we can say is that the Universe seems to go on indefinitely when viewed in three time and motion dependent dimensions. Beyond that it definitely appears to have limitations.

The point I am alluding to is that maybe it is possible that what we perceive as an expanding 3-D plus Time Universe is the side effect of another dimensional structure collapsing and driving the expansion we perceive. Broken symmetry? Now where have I heard of that?