When is it time to stop taking my ALZ (stage 6) wife to social events?

I think as long as she is enjoying it and those at the event are supportive then keep taking her out. You as well you may have to leave her at home though if it is a event where her behaviour may be disruptive to other guests who may not know her or be as tolerant.
You may want consider having a a helper to come with you occasionally so you get a chance to mingle and enjoy the events too, maybe you could even stay later while the helper takes her home.

When is it time? As long as she is enjoying herself and others understand it's not her so to speak behavior and it's not her fault she no longer remembers them, let her enjoy herself as long as she can. Trust me, you will know when it's no longer in her best interest. Besides, at stage 6, she's doing great.

My mother no longer remembered her brother and when we visited him, she flirted... he was the most gracious accommodating gentleman to her.