Saves do grow over time, but I think it is still the Autosave system that is the main culprit for save issues. Reason, the autosaves are created at Cell Load/Render which means the cell is sometimes incomplete when the save is created.
I have never had a save related problem in any TES game or Fallout 3/NV game, but that is because I never use the Autosave features, I never load an Autosave, and I save either before I enter a new cell or only in the middle of a cell but never as it loads or shortly after.
I also never overwrite a save slot more than 10 to 15 times, once I have that many overwrites, I create a new slot. I have also noticed that sometimes a save takes a long time to write, and when that happens, I wait a couple of seconds, then save again in a new slot.