Yes the data sheet limits the value of the timing capacitor. I have used a lot of these with very low failure rates in the actual timers. You can not make a 1ppm timer with them but you do not need a 1 ppm timer if the mechanical part is + - .5 %

I am much to fossilized to even want to do a disipation curve or a point heating evaluation for the die. I just stay well in the design limits and trust the data sheets when my pre production samples work as expected. Of course when they don't it is never my fault there must be an error in the data sheet!!!!!:) Terry