Ok, that second scene makes it a lot clearer what the problems with the first one were.
First of all - turn the subdivision down in the Cloth Surface - having L5 (or L7 like your first scene) in there is a completely ridiculous value and is the entire reason the scene is horribly slow and memory intensive. That should be no higher than L2, if it is needed at all, which it probably isn't. Also you should know that this subdivision is not doing anything good here, whatever level it's on, because the topology of the text is both uneven and triangulated because the intermediate points in the spline and caps settings in the Extrude are not optimal either.
However all that aside, your animation IS doing what you told it to do.
There are 2 keyframes on that object, and they work; text starts one thickness, and reduces from there until next keyframe. There are no additional keyframes, so it stays there. If I add another keyframe after that, inflating it again, that also works for me ! So, still a bit unclear about what you think isn't working here...
CBR