New to vaping

I'm not familiar with that model, but with many vapes they will really slow down vapour production/pretty much stop, that wont mean your herbs done- you give it a stir and it comes back to life.

The taste changes as it goes on, and is different at different temperatures. Different molecules in the weed vape off at different points/temperatures- so the first however many hits at the lowest temperature you get all those citrus and pine type things that you see in strain profiles on leafly and have never got from smokeing a joint. then when stiring stops producing vapour go to the next heat setting, theres some different flavours...
Theres no definite point of its done, but as you go on the taste gets worse and you have to stir it more often to get a decent amount of vapour from it and you'll notice it becoming a darker brown when you do stir- the point at which you give up on the diminishing returns and pack a new oven is a combination of personal preference and how much weed you have available to you.

remember that the vaped herb (abv) can be stored and used for edibles- which means if you do refill earlier than you could have you've not wasted any left over potency, you've just got stronger brownies to look forward to

 

The xmax v2 pro shuts off by itself after five minutes. I don't vape the same weed twice, I save it to make edibles. But you can vape the same herb until it turns a dark brown and/or starts to taste burnt.

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