I would get one that is legal under Spanish law, because if you use the Kimber (10%) you may well find yourself in a heap of trouble, prison or deportation or both depending upon your residency circumstances. better safe than sorry.
it might be that the pepper solution hardens after a given period of time, but that is just a guess.
Agreed on Spanish law. I’m pretty sure their legal system still uses the old “guilty until proven innocent” system.
As far as expiring, I imagine that peppers are one of the more lasting spices in the cupboard and are probably good for 30+ years. The spray might lose some potency, but probably not much. If it isn’t pressurized - how does it spray?