The rough-in valve will likely outlive you, but the replacment parts are just that, replaceable. What might be a consideration is the trim, as not all trim, even from the same manufacturer, will fit older valves, and you may not have choices. While there are some aftermarket places making trim for common valves, not everyone, and no, another valve maker's trim won't fit.
So, unless you want to upgrade the trim, and you can't get it from the manufacturer, or you want some new features not available on what you have, it's likely safe to leave it. Most Moen stuff has a lifetime warranty to the original owner. The cartridges contain the 'working' parts, and that can usually be changed fairly easily. Some Moen valves can be difficult to get the old one out due to mineral deposits, etc, but with the right tools, it's not a big deal.
But, while the walls are open, you'll never have an easier/cheaper chance to update it to something new, if you wish.