I do almost everyday on small projects and not something of great Value either in Time or Money spent.
I don't recommend using anything if you have even the hint of concern unless Failure IS an 'option'.
Now,
I have a gal.cf of UC Clear which is10 yrs old I use out of today and Activator,that's been stored for as long, unopened except when I'm using it currently doing airbrush and odd small projects in a minimum 70 degree shop.
The Activator will eventually get thick and become unusable and I've not seen any of the seeding occur personally, but I reseal the can immediately each use and store inside a slide lock type freezer bag to keep as much Air as possible from It.
Still works "as advertised" spraying fine,no issues with anything other than what outside elements get into it,buffs fine,cures out as usual for Universal clear,still a soft clear,and I'll continue to use it till it doesn't.
Would I paint My truck with it ?
NO !!!
But I will use it for Anything I need to that I might want to.
Yeah,It still works.
Just my Personal actual experiences with It.