I understand that model as the interpretation for inflation, but why do we presume the "balloon" is continuing to inflate at the same rate or faster today than

I understand that model as the interpretation for inflation, but why do we presume the "balloon" is continuing to inflate at the same rate or faster today than it did in the past? It also makes me wonder how we can equate distance to time in a 1:1 ratio. If space is expanding exponentially, then it almost seems like the distance a photon can travel in a given time is decreasing (from the perspective of the observer). I'm probably just confusing myself though.