Judging by all of the dead lighting and uninterruptable power sources I see, I think that the people who build them do not have a clue!
Only way to tell is to hook it up to your unloaded SLA, run it for up to 24hours while watching the SLA terminal voltage. Make note of the voltages every hour or so. If after 24 hours it settles out at more than 6.85V (at 25degC), then it is not suitable for long-term floating.
Your meter should be accurate to 1%. Report back with the voltage vs. time data.