Multiple Fenix 5X Defects - 3 months Old

I have contacted Garmin support about these issues and expect to receive a replacement product. Not acceptable that the HR sensor is defective after such a short time frame....

I agree. A number of people have had this issue across different watches. My 735xyt de-laminated, although it does not seem to affect function. Glad they are replacing yours.

1. I think Garmin are pretty good about replacing it in situations like this.
2. If you set up your Do Not Disturb hours correctly, the gesture backlight shouldn't come on.
4. If you find the battery draining quickly, power the watch down, then back on again - this will often clear stray loops of code that are causing the processor to work harder than it should. Also, check the backlight settings - each 10% of backlight drains around 1.5% of battery per hour. The default 20% backlight would drain 9% of battery over 3 hours if left on continuously.

Really sad to report this but after only 3 months and that's 3 months light usage, I have the following issues:

• Battery runs down really quickly, on a 13KM walk yesterday, that took around 3 hours, it used over 25% of the battery.
  

I would suggest that is quite normal. If I use GPS for any activity my battery use is about 10% per hour. So 25% over 3 hours sounds right to me. If I do not use GPS then my power use is about 0.3% per hour

I can confirm this battery consumption with gps, it is ok. If you need to decrease it, set up gps per 1 s on hiking, it should be stil ok.