You might consider using a regular size queen fitted sheet if that folding bed is a short queen. The fold will be an easier fold with no restriction if the fitted sheet is a tad big.
Also, if you use your rig at roadside rest areas you will need to deploy the slide to sleep unless you have an additional cabover bed. You don't want to open a slide into a travel lane. You might end up with a tri-folding mattress.
It should be comfortable , not many complain about that. As far as additional cost to replace....it will last many years, I would not worry about that.
The rv will start to leak before the mattress wears out.