Improve handling of the user pixel stack

This does: Make the duration to gain stack pixel from X to X+1 identical whatever the situation is. (The time it compared against didn’t changed, and the formula added 30 or so second at each progress, so they had to wait 30 second to gain each one after the first step)

Avoid removing timer progress after placing a pixel (if it was below the max wait time)

Fix the fact it didn’t displayed progress for the sixth stack.