Those work perfectly, I'm using them, bought in 2009.
I will probably be mixing up 1L of working solution at a time,
No! Mix complete 5 liters once. The opened concentrates go bad as quickly as in 6 months or less, whereas the mixed solutions work for years. I use developer mixed two years ago. Store in squeezed PET plastic bottles without air. It just doesn't go bad if stored mixed. Also, you avoid mixing errors and measuring altogether.
Believe me, I made the mistake of mixing 1 liter at a time and trying to keep opened concentrates. The next mix was dead. This is a peculiar process where the EASIEST way of just mixing everything works best.
Even the UNOPENED developer concentrates go bad more quickly than the mixed ones! (Yes, really.) As you are getting four "kits" at once, if you are not going to use them all during two year span, maybe you could try refrigerating those DEVELOPER PART B bottles you are going to store for more than 2 years so that you wouldn't have to see what I and another APUGer found out, unopened part B going bad in 3 years. Part A and C keep better, as do the blix parts.
I would like to reuse the chemistry if possible. Does this mean replenishing, or can the chemistry be reused without replenishment assuming working solutions are stored in airtight bottles with all the air squeezed out.
Yes, you just reuse them. No need to replenish. I have made up to nearly 100 8x10" prints with one liter of developer, no signs of any changes in color or contrast. Just do it.
Strong magenta/red discoloration of developer is normal and is caused by dyes released from the paper, and it does not affect the results.
Do not use a starter. Just mix the "replenisher" solution for 5 litres and use it as is.
The blub on the website talks about using it for completely consistent results
The site is wrong, it has nothing to do with consistency. You might want to use it for replenished machine process or higher temperature process.
for up to 6 weeks, but not left in open trays for more than 4 hours. Have I interpreted this correctly?
This is conservative marketing talk. It just does not go bad. The one I have used for two years, has repeatedly been exposed to air in open trays for days. Maybe I should leave it open as a test, because I have yet to see a way to make it go bad!
Is the Fuji paper suitable for room temperature processing? I've heard mixed reports, but i'm stuffed if not as I don't know what I would do with the huge rolls of paper that are the alternative.
There is ONE report that it is not suitable, and this report is being quoted all the time. It seems there are many more reports of it working perfectly, just like it does for me.
That said, it seems there are many versions of Fuji Crystal Archive. Hence, I can't speak for others. The one I have just works. I use it alongside with Kodak Supra Endura and correct filtration between them by about -5 M -5 Y when coming from Kodak to Fuji. Then, the results are very close.