I don't think it is a new limit, it is just that now there is a little message telling you what the limit is...

I'm not sure whether it deletes ALL the messages if one goes over the time or if you have one more than the limit, or if it deletes one old in exchange for one incoming or if it deletes the ones over a year old or if it wipes out your whole inbox.

I would say... Look for the ones with the oldest date and start saving (and deleting) those first....