Can I leave my T/C plugged in to A/C when not in use?

As mentioned -older chargers or cheaper with no floating circuit will boil your battery dry over the long time.
Even battery maintainers fail occasionally, so leaving one on permanently brings some risk.
My experience is that nothing beats pulling battery clamp as even disconnecting all appliances on the panels, leaves potential for current leaks on the cables.
Disconnected battery will hold the charge for 6-8 months.