Kindling is when untreated seizures tend to lead to more frequent and more intense seizures, and to an overall lowering of one's seizure threshold, over a period of time. So for instance, your very first seizure might be a simple partial, or a complex partial. Then maybe the next few seizures last are complex partials, but start to last a bit longer, and then the next ones after that maybe end up being tonic-clonics, and from there on out the majority are tonic-clonics.
Basically, when your neurons repeatedly fire together a lot over time, this abnormal behavior becomes "hard-wired" and becomes a default path for your brain. So if both your auras and your nocturnal seizures seem to be increasing in intensity and frequency, that might be a warning sign that you should re-evaluate your seizure control.
HOWEVER, the kindling model doesn't necessarily apply to everyone. And in some people, even if they've had many seizures, eventually they might stop having them at all. It's also the case that different people have different levels at which they plateau -- not everyone is going to end up with tonic-clonics. And if you are adjusting your brain environment either through damping the neurons (meds), re-wiring them (neurofeedback), or eliminating triggers and biochemical imbalances (diet, etc.) the kindling process can potentially be negated.