You may want to reconsider transferring your UA RDMs. UA has the largest global network of the airline alliances. Perhaps, look to see if a nearby airport meets your UA needs. UA and its *A partners offer over 18K daily flights to about 1,200+ locations in approximately 200 countries.
In order to redeem UA RDMs for hotel/car rentals, you need to be an elite member. General MileagePlus members do not have that option. I don't recommend using your RDMs for anything but award travel. It's just not a good value; however, value is subjective. Saving your points for a saver/standard award ticket is the best way to maximize the value of UA RDMs. I value UA RDMs between 1.5-2.0 cents per mile.
If you're worried about the RDMs expiring, all you need to do is have at least one transaction with your MileagePlus account every 18 months and your RDMs won't expire. If you have a Chase MileagePlus credit card your miles won't expire for as long as you hold the card.
Without knowing the specifics of your question, I hope this provides at least a bit more information to help with your decision.