I agree with tonikwan.
Regarding the giveups: between players with a higher rating it is not rude at all if you give up if you lost a rook. Actually the opposite is true, it is quite surprising if somebody don't give up in such cases. Professional players always give up the game if they lose a small piece (bishop or knight), because then finishing the game is just routine work, it is not fun. If you want to learn endgames, for example, then you should ask your partner to play the game until mate.