Sitting on anything 14h/day is a recipe for disaster!
You should vary your position regularly (every hour, for example). The simplest solution for this is a desk where the height can be changed easily (maybe with a motor), so one can sit for a while, then stand for a while, and so on.
I only had to use the 'bad' chair because the good ones - with a proper foot rest - had been snagged.
Also, I have an extra Salli Twin I use while cooking and doing dishes in the kitchen.