Super interesting thread.
We have a 20LB horizontal tank in the truck camper. The tank is a 2005 vintage. The tank is absolutely mint condition, without a scratch, ding or rust. Looks factory new. We've only had the tank re-filled maybe 7 times over 15 years.
It is out of certification, and I brought it to our local gas plant (a huge plant the size of 2 Walmarts), and had the guys in the plant take a look at it. They played around with the empty tank for a bit, and said the tank was in mint condition. No charge, no certification. T'was refilled no problem.
Their charge for a recert was $45 Canadian dollars + tax (if it would have needed a valve change).
I'm realistic, and one day, the tank will need to be certified (valve changed) at some point. I was putzing around on the "Net" this past summer, and found what looks to be a direct replacement for our Manchester...called Flame-King.
here-->This Flame King valve "faces" to the right, and my camper's Manchester valve is hosed-up for left-facing tank valves. I found some on the "Net" for between $110 to $130 dollars....considerably less cost than our original 2005 tank.