That's a lot of questions in a short paragraph. I will tackle first, then be critiqued and learn some about the process also when people do respond.
I use white lightning, but my process of cleaning and applying is different. When I finish a ride, if it was wet and muddy. I use a wet spray, while spinning it backwards, I applying wet spray. let it stand a few minutes, then cycle is backwards again with rage held firmly to clean. I do this for a few minutes and inspect. if it is still VERY wet with lube cleaner, then I run it backwards again. Then I apply the white lightning while spinning around to get all the chain covered. I probably oversimplified the process but it works for me. After you do it a time or two. The whole process can be done within 10 minutes easily. I also knock off any chunky debris from cogs and rings.
How long does a chain last? depends on how muddy, how often it is muddy, is it cleaned after muddy, are cogs clean...those may be some questions stated.
For me, I have a bike that I have 10k at least on chain, cogs, and rings. It is my beater winter, bad weather bike and being in Pa, where there appear to be 2 season some years, winter and almost winter, or horribly humid and rainy at other times. (Where else do you put the heater and AC on in the same day, Pa), I just keep cleaning as suggested above on those rainy or dirty mud days. I don't plan on changing until I have a catastrophic failure of chain and I am well aware that I will be replacing all. But as I said. It's a beater and the items I replace it with will most likely be not top notched and mostly used. When I used to race and use high end parts. They needed replaced more often, about 5k miles maybe, and there is a old tip. When the cassette cogs started skipping, flip the chain and you can usually squeak out another 500-1000 miles. I have had only one opportunity to test this theory and advice and it did indeed get me another 600 miles.
Good luck