We have the contactless chip reader and the free mag strip reader, which is free, and I can't say enough good things about it!! I would have gladly paid the $49, but didn't have to because I traded my $29 piece of crap chip reader (Tana, have you written to square yet?).
If you're only using the strip reader (which I don't recommend, but many people do), I would get a spare or two. They're free. Just log in to hardware and request one. As soon as it is shipped you can request another. We have 4 of them, they do wear out. Square doesn't care, for all they know you have a staff of employees using them.