Happy Holidays!
In my experience, the problem with 99% of TPU inner tube is the valve, ever!Too much leaking, no matter the brand.
I've been using a pair of RideNow 24g TPU tubes with clear plastic valve stems in a pair of 28c tyres. They've been great, they hold air really well.
I'll have to reconsider my strong endorsement of the 24g RideNow TPU tubes. One tube of the two tubes I installed developed a slow leak after about 200-300km.
I just had to replace a 24g RideNow tube after a day of use. I suspect I ran over glass as I went through 3 tubes in 2 rides until I found the offending piece of glass had actually remained in the tire somehow. So, I can't really blame the tube. BUT I noticed a bubble had formed near the valve stem where the tube was trying to stretch its way out in the space between the rim and the stem. Clearly, the tpu is just a little too thin to stand up to anything but absolutely perfection in terms of rim, tire, or anything else you send at it. It was one of my last remaining 24g tubes. Most of my tubes are 36g RideNow's but I had 1 or 2 hanging around from an old order.
I have had the same two RideNow 36g tubes in my wheels for over a year now.I would guess ... dunno ... certainly over 3.500km, probably more.They work great for me so far.