I had thought about purchasing a spare LV6548. I still might. But things are moving along with offerings from other manufacturers and if I did have an inverter failure, I might just move to something else that has good reports. The LV6548's I have just plain work, but if any hardware/firmware changes were done, then a new unit might not be a wise decision.
I had purchased two LV6548 a few years ago, then later I got to thinking, as I started seeing China putting a lot more pressure on Taiwan's physical boundaries more than any other time in history, I'd better get a couple more spares (in case it soon gets very hard to acquire more), so a year later I bought two more. They are all four still with the 250v PV input (not the new hardware with the 390v PV input).
I am still super slow and just getting the first two mounted on the wall (working on getting infrastructure and cabling in place), but am making progress on it. I have since decided to install both sets, but keep both pairs separate from each other (in an active/standby topology).
The primary 2P1/2P2 will be on one side of my wall, running normally as the active pair, while the 2P1/2P2 on the adjacent side of the wall will be in standby, powered off and disconnected (presumably forever).
Each inverter has its own battery DC breaker, each have separate 60a breaker into the AC breaker panel, separate 60a AC input breakers (for optional gen charging), and I'm installing a pair of 4-channel transfer switches onto the PV runs, so I can flip an A/B switch (at zero current) to move the PV power to the adjacent pair of inverters.
I guess that's my goofy geek project of the year though. Probably 10 years from now it will be all different equipment on that wall, but you never know, maybe it will all become worth it someday.
I've never been bit by keeping cheap spares of tech gadgets around, available, and ready for immediate use, so you can wait til Monday to fix a problem instead of having to cancel dinner on a Friday night to fix something.
I have been working with a lot of my off-grid neighbors installing, consulting, and troubleshooting on these newer systems with super duper capable inverters, and even like the 18kpv and wall battery, and they all look tempting and slick, but my money is already planted in my DIY game, and since I am a mechanic at heart, I don't mind having a somewhat legacy system, with a few more knobs. Perhaps someday when all the neighbors decide to upgrade, I'd just buy some of their equipment used, but for now, I'm still stoked about these LV6548s just fine, and my DIY batteries.