In any case... better to use the available stockpiles until they are not good anymore. Number of missiles and bombs are not infinite and training with what could be used is always a good idea. Training with them is probably has valuable than training with newer types anyway,
Unless you are doing live fire exercises training rounds are always better. Every time you carry a missile into the air you are actually using up its lifespan even if you don’t fire it. I recall an episode of Chinese military report that showed JH-7 firing dozens of AA missiles. Pretty sure they wanted to use up the PL-5s before expiration hits.