Cartridges last a long time. As for break in, some people use special break in records that stroke the electrons in the tight direction, or other tone generators with a special connection through the cartridge. But the non-fetishists and the merely obsessive all the way to just plain lazy figure a couple dozen plays will do the trick. You know it needs replacing when either you start getting bored or you upgrade other things so that you can hear the difference. Needles [sic] are another matter. It depends on how much you drink while playing, or doing other set-up tasks. With modern tracking weights, a gram and a half or so, and with the cleaners for both needle and records, including something like Last preservative, you cut down the friction down so far that you can get well over a thousand hours. Again, set-up goes along way. You know if it is bad when Maria Callas sounds like Tom Waits. Probably a chip or other gross failure is making really god-awful noise. Otherwise they just kind of fuzz out from gentle wear. Brush your records and the needle between plays. And I don't know anything about specific replacements because I always look for an excuse to get the next hot little number.
