45 minutes can be a lot if you keep it in hand over night for sleep tracking. You'd then need a to find a 45 minute slot every day to charge it and be consistent with it. With one day battery life you can't forget to charge it every morning for example. Or what if you didn't bring a charger with you for an overnight trip? Anything less than a full two day battery life is a deal breaker for me.
I've found the iPhone notifications to be very handy in this regard though - I throw my watch on the charger when I shower and then pick it up whenever my phone notifies me it is done charging.
It takes 8 minutes to charge for a full night's sleep tracking according to Apple. That's about the time it takes to wash and floss your teeth coincidentally :)
I usually take my AW2 off when I wake up and put it in the charger while I do my morning stuff. Same with showering etc.
