Title says it all.
I have the same number of messages a month ago......and it took a looooong time to load. I suggest you backup your messages using "SMS BACKUP+". It's a free app, and it will backup all your messages by uploading them directly to your GMAIL Account. They will appear as individual email messages. Do not worry....it will not flood your GMAIL account, as it will transfer the messages to a separate folder/location.
After backing up my messages, I deleted my old messages by setting the Text Message Limit to "100 messages per conversation" (of course you can set your own limit)
My phone runs smoothly now.
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