Even trojan's group 27 is rated at only half the total cycles as the t-105's. It is still a marine battery. How hard it is to max out the SG a deep cycle is unknown until someone actually accumulates some data.
but most with flooded 27s should likely avoid the hydrometer and just complain properly when the time inevitably and prematurely comes, where they' no longer hold a charge' and need to be replaced.
'Ignorance it bliss' has more value when one is cycling flooded marine batteries. They are 'Just fine' until the day they are not.
Cue the long lived group 27 stories, but with no data as to how many and how deep the cycles were.