Natural Herbal Tea

I will make a toner with natural herbal and use vodka as a preservative. How long does something like this last?

It depends on proof of vodka (is it 80? 100?) The water / tea and added that the final alcohol content of the mixture will be. When making dyes, it is advisable to have a minimum alcohol content of 20% to prevent tampering. It has a lifespan of several years. For your purpose though, which seems quite high for something that goes on your face.

Personally, I would not use vodka or other alcohol on my face. It is too harsh. I make my herbal tonic by infusing dried herbs in the witch hazel distillate for a few weeks of effort, then adding 1 part flower water / hydrosol (like rose, lavender, chamomile, etc.) by 2 parts Witch Hazel infusion. You can then add a few drops of essential oil. Make sure you shake well before each use to mix the oils, because they float to the surface.

I hope this helps.