How long has your JR Backup battery lasted?
If you don't have a datasafe and you attempt to change your own memory battery, first bridge the battery holder + and - connectors with clip leads connected to the correct voltage and polarity of an outboard backup battery.
Then, remove the old battery and replace it. Remove the clip leads and you're done with the memory intact.
My JR's are only two years old, so in another three years I'll give it a try, but this is standard procedure for keeping memory while changing a memory backup battery.