Random ramblings that may be known and/or no use...
In Iron Coffins Werner talks about snorkels, desperately wanted one. He chatted with another commander who was (supposedly) getting a boat with hydraulic torp loading, a fancy snorkel, and other goodies. Presumably yes, there were updated snort models. Werner got a snort 5 mins before the war ended, and had a few problems:
"Then a sudden vacuum prevented me from questioning him. The float of the Schnorkel had jammed in closed position, and with the air intake cut off, the port engine had sucked most of the air out of the hull before the diesel could be halted. The Chief's orders died in the thinned air. The men gasped for air, their eyes bulging out." Later he describes taking on water, 5 tons i the mast piping and 20 in the diesel compartment. U 865 reported by radio their snort was defective and unable to dive, bombed. (They sunk). Later again the sort mast was frozen, broken cable. It was frozen erect! This was the cable-raised type, prolly early model.
The snort porblems continued for years with the USN (at least thru to the early 60s). My former Cmdr mate tells of the auto-cut-off valve on the float constantly shutting (to prevent wave flooding) - it would stop suddenly, and the diesels would keep sucking air anyway for a couple heartbeats, and during that short few seconds you'd get a vacuum jus like Werner experienced. Not sure if it was ever perfected for the USN, but now they have nukes. (I would be a tad nervous with a reactor on the other side of a bulkhead. They store emergency diesel in a tank between because apparently it's good at absorbing the stray radioactive bits, but...Diesel Boats Forever!)
The Aussies have snorts on their boats, and I guess they work well enough. (New German boats, at least two, use fuel cells in addition to batts, so don't need snorts, pretty cool).