Is the 9000maH battery worth buying? Or are there still issues with those who have this battery? I am trying not to sell my V10 just to get better battery life

(I've 3 portable power banks too....)
It'd be great if a few users could chime in and confirm that their batteries are working alright. Thank you!
Regards,
Vishnu
First off no matter what battery you go with the Snapdragon chipset in this phone is a hot power hog and LG seems to have hard coded the stock battery capacity in the kernel to 3000 mah. That doesn't mean you can't ever use a higher capacity battery but to get the best result you need to do either a factory reset or have a rooted device and delete the calibration file.
I bought a Zerolemon before marshmallow was released and I had not done a reset to clear out the battery calibration, so I noticed the calibration seemed more than little off at times. The phone would not stay on below 3% yet when I temporarily pulled the battery it would power back on and sometimes show as high as like 20-30%. I'm not sure how much you know about charge state estimation but battery charge state is factored by battery voltage so in the short time the battery was pulled the voltage was able to recover slightly once the power load went away. Then when the phone was powered on the capacity algorithm detected the higher voltage, did a capacity estimation based on the calibration file and decided there was actually more power remaining.
Resetting my phone when moving to Marshmallow seemed to help the situation in addition to not swapping back to the stock battery as that WILL mess up the calibration but it still felt like I wasn't getting full capacity. I ended up doing another reset or two and stuck to some charging guidelines that say to never let the battery drop too deeply below 20% if you can avoid it, otherwise you risk hurting your capacity. I've read more recently that if you're charging from a portable battery pack to only charge to 80% and not bother trying a full charge because that last 20% requires more energy than the charge up to 80%. If you absolutely need to top off to 100% do it with the phone off.
My most recent reset was at the end of December when I rooted my phone so there might still be some apps missing from being loaded in the background but now that I'm the good charging habit I usually see well over 12 hours before even hitting 20%. I've also gone well over a day simply from lack of use and forgetting to plug in my phone before I go to sleep. GSam Battery Monitor is showing Average Battery life per complete charge is 22h 55m (13h 30m Active) with Screen on average of 4h 46m (14h 15m Max) and those stats are since Apr 29, 2016.
One thing I should mention is the battery I originally bought had a badly soldered connector that eventually broke off after a couple months. Which I think could have contributed to the seemingly weak capacity I was getting. I contacted ZeroLemon, sent it back and they sent me a whole new battery, no charge since I was still well within the 180 day warranty.
I have a single 20,000 mah portable battery that I carry all the time and I recently received a quick charge adapter for in the car. If I know I'm going to be at a place that has a power outlet available when my battery is getting low I take the stock LG quick charger since it takes so much longer to top off the 9000mah battery.
Going on almost a year with a ZeroLemon my only gripes is there isn't NFC support and a more rugged Otterbox style case that'll work without modification. I did buy an NFC sticker that I got to work and an Otterbox but I've been too unsure at where and how to cut it cause it's a bit awkward to get the two halves of the case lined up. I probably just need to take the time and make some kind of holder to keep the top and bottom of the case lined up while I mark where to cut. Just based off of a dry fit I'm pretty certain it can be done but it could make the bottom of the case a bit weaker.