philsknees wrote: Both of the Exped UL's I've owned have suffered internal baffle failure sufficient to make them unusable - "Like sleeping on Quasimodo"
It has become obvious to me that inflating by mouth introduces warm moisture air into the mattress which eventually condenses affecting the glued internal baffles, leading to their failure. My experiences point to this being more of a problem if the interior insulation is constructed from wadded material (Exped) rather than a reflective layer (NeoAir). That said, it's much better to use an electric inflation device, pump bag or similar with either.
It's somewhat academic, but I don't think that description is accurate. I used to manufacture in PVC fabric, in a completely different field and on a different scale, but the principles seem the same. Mats are more likely to be high frequency welded than glued, but either way the fault is a separation between the base material and the coating, rather than between the bonded layers. This isn't effected by moisture, inflatable dinghies are made it the same way. Faults nearly always originate at the end of a seam, once it starts to lift, that's it, a child could pull it apart, though trying to pull it apart in the other direction is a different story. In most products there's access to the end of a seam and it's possible to do something counteract this - look at how Ortlieb panniers are constructed, with something stitched across the end of every seam - the best you can do with a baffle is to increase the size of the bond at the end, which is already done, though there's a limit.
This isn't to say that every single mat will fail, I doubt the manufacturers would tell us the figures, but this method of construction is more prone to failure than others. I'd like to see a mat with separate air chambers and no baffles, it'd be heavier and take longer to inflate, plus you'd need a way of equalising the air pressure, but I think it would be more reliable.
EDIT - photo from a training manual of what a good weld should look like, once started it's no harder to peel like that than an orange.