I expect the service life of these J-15 aircraft of various varities in to be more like 25+ years in PLAN Naval Air service aboard its carriers.J-15 is likely to have catapult-launch abilities since the PLAN wants it to be a long-term fighter until the 5G jets come into service.
With the development of the J-15B as well as the J-15S (there's a rumored J-15G for EW), it's pretty clear that they are planning ahead for its entry into service for at least a decade.
If they build the two-seater strike version, and continue to upgrade and improve the single seater...and then add a dedicated EW version (like the E/A-18 Growler in US Navy service) then you can bet that 10 years would not nearly be enough to justify all of that. Those J-15s are here to stay for a good many years...and they will be fine aircraft.
The F-18 Hornet, which has been superceded by the Super Hornet for quite a few years now, and will be replaced in full by the F-35, has already seen 35 years of service. Why? Because it is such a good, well rounded, and multi-role platform. The Super Hornet will carry on in that tradition, and then the JSF, Lightning II behind it.
I expect the J-15 will fit that same mold.