exiting Bolivia for with only 30 day objeto determinado

Hello, I am in a strange predicament that I am sure others have been in before.

I arrived on the 18th of November with an objeto determinado visa that has a validity for 30 days (expiring the 19th of december). my NGO here is going to ask me to send my passport back to La Paz (not where I am) to continue the processing of the visa and its extension. My problem is that they have not yet asked me for it, and the day of my travel home is getting closer, I am going to fly home for Christmas on the 22nd of December. I am a little fearful of sending my passport away just before.

What will happen if I do not send it away, and go home for christmas but need to return for another 4-5 months in the new year?

Will they let me back in? or can I extend the 30 day objeto determinado?

thanks for all your help

Ari Fries