I think you've vaped too much when you get past the solid nic buzz and you start to feel sick. Now if you stepped down your nic level "vaping too much" would take longer to get to.
If you vape the same flavor constantly, eventually your body will adjust to it and you will lose your ability to smell or taste it, that would be vaping too much but switching flavors every now and then will fix that.

I'd vape Honey Pearry all day every day if I wasn't scared of desensitizing myself to it.