I've always heard that fast charging is fine as long as you don't go over 80% of the battery's full capacity. The Luna charger puts out 5A but switches off when the battery reaches 80%. Or they can switch to a lower amp setting if you want a full charge.
In my case I don't want to spend hundreds of dollars on smart chargers if I can do the same thing manually with a timer. I'll just check the voltage and if the battery is 50% then I can safely add 3 amps and set the timer for 45 minutes.