To me,'three to seven' implies that whatever it is will stop at seven o'clock; 'three through seven' suggests that it will continue at least until seven, and may carry on beyond.

The expression I find irritating (for no very good reason, I admit) is 'horseback riding'. If someone says 'riding' I assume they mean 'on a horse' unless they, or the context, has made it clear that they mean a bike, camel, bus etc.