I really like the last one, it is really true. Having a friend is having someone who you can count on. So the nicest thing you can have, but for having a friend means you also have to be a friend. So it makes you a better person :) The first one is also nice, but I don't like as much as I like the second one. But it still true we will be learning until the day we die :O

I like the second one.

关于学习： 活到老， 学到老。 关于友谊：海内存知己， 天涯若比邻。

both are very nice , especially the first one cuz its my last year in uni and i sure do feel like it