I've only done a lot of reading, but have perceived a consensus on this issue. Supplying lower currents than recommended over longer time periods is in itself unlikely to affect longevity.
However assuming these are "native" LFP4 cells, perhaps with balancing and UVP/OVP circuitry but not "lead drop-in replacement" style, the key to longevity is NOT pushing voltage up high, and NOT trying to get top level SoC.
With short charges from a high-output alternator, best practice for longevity is 13.9-14.0V; .3C to .5C current is actually ideal if you can manage it, and then STOP when current drops to .02C.
With lower-amp inputs, over long periods as from solar, the CV max should be lowered to 3.45Vpc or 13.8. Resting voltage should settle to around 13.6, which will be within .1% SoC from what you would get charging harmfully over 14V, but much gentler, and require less frequent balancing.
Ideally you don't float at all for longevity, but if you do "have to", then bring it down to 13.2v (3.3vpc)
Never draw them below 20% SoC.
When not being cycled regularly, let the bank rest at 40-60% SoC, never "full" (resting >= 13.6V)
Never allow any charge input when cells are under 40°F.
With this sort of coddling they will likely last at 80%+ capacity for well over 2000 50% cycles, maybe 20 years. But of course no one knows yet.