I just noticed that if I go down to 300Ah of lithium for my house bank, then 120A of charging current would be 0.4C, like dreadlocks said I should shoot for.
There is no harm in a **lower** C-rate, only higher.
When the temperature is cooler you **must** reduce your C-rate, down to even 0.1C
so a bigger bank lets you charge at a higher amps rate than a smaller one.
The idea of "takes longer to get to Full" is silly, leftover lead thinking.
LFP longevity is harmed by sitting anywhere near Full, much better off
cycling with the Ah per day you need, centered around the 3.2V midpoint.
IOW having a bit more capacity than you usually need, might triple your bank's lifespan.