I knew there were other benefits, especially cleaner burning. The only thing that I've read concerns about is cylinder and maybe valve wear because LPG/CNG burns so clean. I guess when you have to take yours apart we'll know!
Cylinder wall wear is universally claimed to be minimal. No wet fuel to wash oil, no micro-abrasives from burned oil seep. Since oil also stays VASTLY less contaminated (no contest; the oil on my 200K+ mile 232 stays like-new up to 5000 miles) it continues to lube parts like a just-assembled motor.
While there is a different burn pattern to the fuel load, which I'm sure changes the exhaust mix and temp, there's simply the same BTUs per cylinder load driving down the road; total heat output is the same as gasoline, even if peak temps are higher, the heat isn't (eg. you can put a 700-degree match out between your fingers (low heat); burn your hand on a spoonful of boiling water (high heat)). Valve mass is the same. Could probably improve valve lip cooling with camshaft.
I dunno, my engine runs OK, I'm not gonna tear it down from curiosity. Maybe I'll fix the head/compression and find out then. Someday if I drive to someone's place and they have a borescope maybe a look-see down a plug hole or down the distributor hole would be interesting.
The 72 Hornet gets the Rambler's used spark plugs -- they look like new. Probably shouldn't even change them. I heard some fleet places run the used LP motor oil through their gasoline vehicles.