I cannot believe that this would be the reason for NOT doing a refurb. People will complain if it's down for safety reasons. People will complain if it's down for a refurb. People will complain if it runs slow. People will complain if they are fixing that ride over this ride. People will complain if a drop of rain comes down. The theme here is that people will complain if things aren't 100% what THEY want not considering that what they want is different from what the other person wants. Then that person will complain.
Point is, is that Disney is probably used to "Complaints". I suspect the repair/refurb schedule considers many other things. First is Safety followed by "Profits" (which probably has a small consideration of the complaints), then other factors such as a larger plan to replace something, budgets, etc...
So while complaints are going to happen I suspect it's only small factor. The budget/profit is probably a bigger one which is evident in that they are using a "Used" sound system.