I don't have the same experience as others with flooded deep cycle batteries (I've been using sealed AGM for 10yrs or so), but because you shouldn't push sealed AGMs up to 60v, I found that they do equalise at a lower voltage - but it does take longer.
with my original solar-only setup using 'yuasa endurance' AGMs I never went over 13.8v (12v battery). on long sunny summers days the battery would equalize over several days of sun, but in the winter I would periodically give them a continuous 13.8v over 24hrs (from grid power) to equalise them. nowadays I have hydro as well as solar and equalising isn't an issue despite never taking them over 13.8.
In theory flooded batteries should also equalise at the lower voltage, but having said that, flooded 'traction' deep cycle batteries might require more equalisation than AGM's (I think yuasa literature for my batteries say they make a point of using close manufacturing tolerances to keep the cells matched). I guess for you it depends on how long your battery will have to equalise before you start discharging it again - If you're using solar only and you deeply discharge every day, then you may have to periodically do an equalisation at the higher voltage; if you have wind/hydro and solar you may find they equalise OK when they see an extended period at 57v, especially if you don't deeply discharge every day.