How Long to LPG Regulators Typical Last

CatDaddy

Last fall I purchased a 2022 320S BD from the original (first) owner. He claims he put less than 6k miles on it. On the way home from picking it up, I stayed one night in an RV park. The heat worked, but I was connected to shorepower, so it probably was using electricity for the heat. I'm not sure how the priority was set on the Alde system.

In preparation for a shakedown trip, I tried firing up the stove and the Alde system on gas. I couldn't get either to work. I could not hear or smell any gas at the stove with the Alde system off. I'm pretty sure that zero gas was flowing. The previous owner suggested that the excess flow valve in the pigtail might be stuck closed. I disconnected it from the LP regulator and cracked open the LP tank valve. Gas flowed just fine.

I also tried a second LP tank with no change.

That really only left the LP regulator so I went to a nearby Ace Hardware and bought a vertical-mount, two stage LP regulator, some LP approved teflon tape. The regulator I purchased is a two-stage regulator sold under the brand "Mr. Heater", but the name on the casting was "Chen Fong". I installed it in the trailer.  That fixed it; the Alde and stove fired right up. 

Which leaves me with a few questions for the forum:

1. Would one reasonably expect the LP regulator to fail after less than three years of very light use? I am not impressed.
   
2. The OEM regulator installed in the trailer was marked "Fairview GR-9950XF". That part number doesn't appear on the Fairview website or anyplace on the internet except eBay which makes me think it is an outdated part number, but presumably the "XF" indicates "Excess Flow". Fairview says their two-stage valve with excess flow control is GR-9554. If the excess flow valve is in the pigtail, do I need another excess flow valve in the regulator? The regulator I purchased at the hardware store does not appear to have excess flow control. Do I need excess flow control in the regulator?
   
3. Is there a better, more reliable, longer-lasting LP regulator I can buy?
   
4. Is the black cap on the GR-9950 just a dust cover? It was a bit loose when I remove the regulator from the trailer.
   

Thanks for your help!