Are you sure the Level 1 charger is better for the battery? The manual implies the opposite, it recommends using a level 2 charger as often as you can.
I use a level 1 charger exclusively, but that's because it's not practical for me to use a Level 2 charger right now. If my circumstances change and I can install a Level 2 charger, that's what I'll do. Both for charging speed, and because it's what I've seen Kia recommend.
The manual is trying to avoid all liability for poor house wiring. Level one is fine, but should still be on a dedicated circuit.
The whole question about which is better for your PHEV battery, level 1 or level 2, deserves its own thread. A lot of confusion on that topic on this forum, and I think Kia needs to explain their recommendation that level 2 is better than level 1 for long term battery life. Personally, I still consider level 1 to be better for the battery in most scenarios, and I think some of the confusing Kia guidance might be misleading.
I was shopping for a used car about four years ago and I fell in love with a used Honda Accord HEV. The only thing that put me off about it was concern and unfamiliarity about the question of battery life. I didn't wind up buying it (because the sales guy was a jerk and because I wouldn't meet his price, but I did want it). I recently read that the cost to replace PHEV battery out of warranty exceeded the average cost of replacing an ICE. Yikes if true.I don't own a plug-in Niro, so for me it is a non-issue. But you also might want to consider the side of technology leap when looking towards the life of your car. Sure it would be nice to have a car that will last you well beyond the 10year mark. If you were a person who having the car last far beyond the 10-year mark for financial reasons, then I would seriously question why you would be buying this type of car in the first place. the Niro is not a cheap car. I have owned several cars over my life and have driven one of them for 13 years. it was a great car to own, but to be totally honest, the vehicle that it was replaced by was so much more technologically advanced that it was by far a better choice to ditch the old one and not fix it just to get something that was safer. It was a 1996 Ford Explorer Sport. and it did have ABS but not airbags. There was rudimentary traction control, and it was built on big steel but on compartmentalised crush safety zones etc. I replaced it with a 2006 Ford Escape that give me full curtain airbags, crush zone safety cage protection, traction control, rear backup sensors. It was that much more safer a vehicle that it was worth just repacing. I mention it as you are worrying about a battery that will likely die and need to be replaced in 10 years as you PHEV will not give you nearly the plug in distance that you'd like to get. It will however likely run just fine as a regular HEV. But in 10 years they will likely have developed new battery technology that supersedes what is offered today. There will also be new safety technology that will surpass what is there now and likely be worth your while to simply dump what you have as what is new will be just that much better the cost-benefit will more than justify the expense.
You've rightly listed some technology advancements that will surely come along in the next decade, but I think you left out one that might affect all of us. I imagine that as HEVs and PHEVs (and especially EVs) become more common, the ability for technicians to assess the current and future battery life span of a used car will improve, and that will affect our ability to sell our cars to a dealer or a private party in the future.
I believe that economics are important to most people who own Niros, even if they aren't necessarily the most important factor. I didn't exactly buy this car to save money, but I wouldn't have considered it if not for the financial incentives, probably would have purchased a used Prius instead. That means that I want to have a low cost of ownership, and I want to have a reasonable resale value at whatever point I choose to part with it. It seems to me like the battery health is likely to be a major factor in a car's resale value, someday in the future, even if most people don't really know how to assess that question today.
One article I read recently stated that a lot of people who are thinking about EVs and PHEVs are leasing rather than buying, for the reasons you mentioned: today's battery technology will probably be significantly improved a few years from now. I usually think of leasing a car as a way to throw away money, but perhaps the current state of battery technology is such that it actually would have been smarter to lease, rather than buy.