How long will the internal battery itself last before it needs replaced? topic

I see a lot of threads about how is the battery life, but I want to know how long the life of the battery would be expected to be? This is my first phone that's had a non user replaceable battery and it made me wonder how long this battery will last me and continue to hold a solid charge?

I know there are variables, and my variable is I only charge it once a day at night on a Qi charger (I know i've read the heat can effect the battery), but surely its the same or less heat than the turbo charger produces I'd think.

What are some realistic life spans on these batteries based on perhaps a moto x history maybe since its similar? It doesnt seem the battery is readily available to purchase on ebay or amazon since the device is still new. When the time comes I'll replace it myself, just wondered of any comments you all may have from experience on similar devices?

Thanks!