The body could last your lifetime...the cartridge and trim certainly won't. I don't know when they instituted the federal requirement for anti-scald tecnology on showers, but if yours doesn't have that, I'd certainly change it. Some people love Moen, but there are lots of stories about people having great trouble trying to remove the old cartridge to replace it when it finally fails. They'll give yo ua new one, but so what if it costs you hours, or the cost of a plumber to do it?
With a remodel, I'd rather opt for replacing the valve. Then you'll also have more choices about the trim. Personally, I like Grohe, but many of the pros here like the Delta 1700 valve body. I really like a thermostatically controlled shower valve...set it for your preferred temp, and it stays the same winter to summer...beginning of the water in the WH to the end. That's available from most companies, and is an option on the 1700 valve from Delta.