Hi Rajender,
It's probably not going to change anything but:
1 - You can actually have 1000 message per message class (from 000 to 999)
2 - You can have texts ids from different message classes in one exception class, which means you are not limited to "only" 1000; rather you can create as many as you want up to the technical limit (about 16000 as I said. If you want to be sure go to menu class->check->generation limits).
Regards,
Custodio