My banks of SLA batteries' primary function is as a backup store of energy for when we have a grid outage. They spend their lives on float mostly during the day, rest overnight, and are ready to jump into action as soon as we have a grid outage. They are purpose built for that very task in data/telco centres and by getting from there I was able to access a pretty decent chunk of capacity for not a lot of $.
I don't care about number of cycles as they are hardly cycled and they'll age naturally first, at which point they can go to the battery/lead recycler. Using LiFePO4 for that job just seems an extravagant waste.
I am however considering adding some more functionality to my system, having it manage regular overnight household loads but I won't do that until I add some LiFePO4 to the mix so it can manage the daily cycling task while the lead sits there ready for backup duties. 5-6 kWh worth would do the job nicely.