I used the Outex kit for my 2020 V7III Special rear wheel and I have around 9,000 miles miles and one tire change in that time. Initially I had a slow leak around 2 nipples and my tire guy recommended I try slime highway tire sealant (they make a few versions) and to make sure I spread it on the spoke side of the rim. I haven't lost significant pressure since. I add a few pounds every few months. I buggered the installation slightly and knew it when I did it so the 2 spokes leaking was not a real surprise. I haven't wanted to devote an entire day to doing the front wheel so I just pumped that tube full of Slime and have been lucky so far. I have a friend that did Outex on both wheels on his Royal Enfield 650GT and his has been perfect for 2 or 3 years. Anyway you do it, prep, prep, prep is key!
Scott