I've noticed some trends with failures on beaded tants. With some exceptions values 10uf and lower seem to hold up well. It's the 15uf to 47uf tants that seem to fail the most. With 47uf being the worst of all. Has anyone else noticed this?
Yes. I suspect that it's down to physical volume. Crudely, capacitance * voltage rating ~ volume. When you're making small caps there's less room for optimising the quantity of materials you're using, as the caps get physically bigger it become easier to minimise the volume of materials used. You've probably got a fixed mechanical tolerance you can work to, on a small cap this might represent 10% of the value, on a large cap 1% of the value, so for small caps you have to play safe and aim for the high side of your tolerances. For larger caps you can get 'closer to the wire'. To put it differently, based on fixed physical tolerances, a 1uF 6.3V cap the voltage tolerance might
* be +2V, on a 47uF 25V cap the voltage tolerance might also be +2V, so you get +32% and +8% voltage tolerance respectively.
Once you get bigger than some specific size your intended physical tolerance gets bigger than your quantum of physically achievable tolerance and it becomes a controllable parameter again. Hence that hump in the middle.
*Totally made up figures.