A lot of things I've done haven't realised their immediate potential for maximum damage, but over time have lead to issues. For instance after 4 years of light but regular using a chain saw, I now get pins and needles so I suspect I've been using it too tensed up. So I don't really worry about lethal doses when mixing my own e juice, but I'm more worried about whether I've slightly leaky chambers leading to a long term low level exposure which may lead to problems in a decade's time.
One day later I'm adding this edit, I've been worrying about e juice smears on my fingers for a couple of months now, and wondering if it's got any long term consequences, but I'm just thinking that low level smears are probably the same as a nicotine patch and while it'd obviously be best to clean up, its not worth getting too paranoid about?