Just a reminder that this one hasn’t been answered yet. I had been expecting arguments in favour of both approaches but, so far, no one has ventured an opinion.

LifePo4 Batteries are best used between 20-80% SoC window.

No need to recharge them fully with every "cycle"..however every once in while (once per wwek or even month), you should charge them to 100% in order be balanced and BMS (re-)learning the full state.

my 2 cents.

The manual, page 39, covers it very much. Lithium batteries typically don't benefit from float and neither require full charge cycles like LA. Think of mobile phones. The cell balancing is important.

"Float" is a lead-acid battery term. Lead-acid batteries need continual charge current because of their high self-discharge rate and their vulnerability to sulfation damage when not kept fully charged. For LiFePO4 (LFP) batteries, I prefer the term "SOC floor" (though none of the chargers use that term). And the only reason to keep LFP batteries on a charger is to get some backup power utility from them if shore power fails.

When on shore power, I keep my 12.8 volt nominal LFP batteries at a terminal voltage of 13.15 volts, which equates to about a 50% SOC floor. Calendar aging is reduced at this lower SOC, I still have half capacity during a power outage, and less waiting time to recharge the batteries before getting underway. It's a compromise, like everything else in engineering.

I do not recommend setting a SOC floor at nearly 100% SOC because calendar aging is accelerated at that SOC. But if you feel you may need 100% capacity during a prolonged and probable loss of shore power, then I understand why you would accept the compromise of calendar life versus utility.

There is an excellent discussion on SOC versus calendar life here: https://nordkyndesign.com/practical-characteristics-of-lithium-iron-phosphate-battery-cells/ under the section titled: "Impact of State of Charge and Temperature on Capacity and Cell Life."

Daily cycling of your LFP battery with a solar charging source will subtract from the battery cycle-life, but the effect is so small in proportion to the LFP cycle-life expectancy that I wouldn't worry about it. Just be careful not to overcharge the battery. I have my MPPT set to 13.8 volts with a tail current cutoff of 0.014C (1.4 amps for a 100 AH battery). It is CIRITCAL to set a tail current cutoff. You cannot detect 100% SOC of LFP batteries using terminal voltage alone while charging. Any charge voltage at or above 13.5 volts is capable of overcharging a 4-cell-in-series (4S) LFP battery. Here is a discussion on that issue: https://nordkyndesign.com/charging-marine-lithium-battery-banks/.

I cringe every time I see YouTubers charge their LFP batteries until the BMS cuts off charging. If you do that for every charge cycle, you'll end up with bloated (gassy) cells and premature battery failure. The BMS cell overvoltage charge cutoff is an emergency protective function intended to prevent abusive destruction, but it's abusive nonetheless and not something to depend on for every charge cycle. The cumulative effect will be a drastically reduced cycle life.

@Allan Fraser

With lithium it is use or loose it.

Use the bank in the operating voltage range and temperature. Most lithium's have an energy life cycle as well (energy in and consumed).

Calendar aging also becomes a thing anyway so even on 'float' they are consumed. There is also a thing with lithium s keeping them at one voltage causes dendrite formation. (So best to use them)

Thanks very much everyone. Very consistent so particularly helpful.