I always assumed blinds up for take off and landing so that whatever is outside is also the same light inside in case there is an emergency you're used to the lighting. If blinds were down during the day, you're going to be dazzled going outside, vice versa when the lights are dimmed on a night flight.
I did a cabin crew course at college - my tutor was ex BA long haul crew and that was the reason she gave.
I have heard of cabin crew turning the heat up to get pax to sleep. Some can't be bothered, same with any job I suppose
Someone mentioned the emergency lighting on the floor, that stuff is USELESS!!! I have to point it out!
I've doned (spelling?) a smoke hood, been in a cabin full of (albeit fake) smoke and in the dark and honestly it's nothing more than a faint glow.
In the panic of everything else I don't trust these to help and always make sure I know where to go beforehand.