trickle charging how long?

[Ron07x5]

I have a "smart" agm compatible trickle charger. I have used it to maintain the boat battery off season. So I am now running an experiment with the charger on our 2007 x5.

The charger charges at 0.75 amps per hour. The x5 has a 6month old battery installed by bmw. The x5 is driven maybe 50 miles a week unless going somewhere out of town. In last.weeks.we.haven't.used out.of.town.

So the charger has a red led meaning I am charging and a green it.is charged led. So far we have gone 10 hours for a total of 7.5amps in and it is still showing it.is charging. So how long til it show fully charged how many total amps in?

So one.would think it should have topped off the battery by now? But I have read about these cars losing battery charge over time especially with short to the store trips and especially with the twin turbo v8s. True? Note this one is a non turbo 4.8 v8

So opinions? comments?