Battery life?
My experience has been varied, some batteries seem to last forever and then some fail within a month or so of replacing.
I've started writing my accumulated milage figures down monthly so I can reconstruct as much as I can if they fail.
And I've heard equally bad stories about the wireless units, eating batteries or early failures. These units have to use more power than the wired types.
For a particular battery type, ie, 2032, do a google search and you'll find them 10 for $8 or less, probably better than the ones that have hung in the drugstore for 6 months at $4 apiece.