My battery does seem to drain a little faster since getting Whoop a month or so ago. We know that there were background issues that seems to solved but I still see a faster drain.
But some thoughts.
How many percent you are losing in 24h? In my case it varies between 7% to 10%. In last 48h lost 19%. 5.0 will never last 14 days 
Shoot, I am talking about my phone not Whoop it’s self, I should have been clearer. I will change the heading.
As for the Whoop 5/MG lasting 14 days, I highly doubt it. But I will monitor it and keep you posted. I just charged it an hour or so ago.
I reached out to support about it recently, they told me to reboot the sensor. Now I get the 14 days. If you haven’t yet, maybe try that.
I am checking mine now, 4% drop since 5pm last night, 15 hours ish. So pretty good.
But my issue is Phone battery drain not Whoop battery 
My Phone Battery drain isn’t excessive and not worth a support ticket. These are just thoughts..
Since Whoop is new to me, maybe I am more engaged and have the app open more.
Since the dark mode is always on, I find I need the brightness up more during the day to be able to see Whoop clearly.
Always Open in background exchanging data 24/7 is maybe not ideal.
My guess is 2
