My town and country has had a new battery and alternator installed in June of this year. If I let it sit for more than a day or two and not drive it, it doesn't want to run

SOURCE: When I drive my Chrysler Town & Country into the freeway, the rpm

Check for code s
cycle key on off on off on
read codes in the odometer area
check tranny fluid
most common input and out put sensors
and in some cases the solenoid pack on the side of the tranny
codes will help in determining what is going on
let me know

SOURCE: good alternator & battery, but battery goes dead just sitting

The regulator could be sticking in the alternator. Unplug the alternator and see if the battery goes dead. I replaced an alternator once and the new regulator was bad.

SOURCE: I replaced the alternator and the battery in my 97 Town & Country

check fuse and fuse links.you alternator is not receiving power .you have a open fuse or fuse link.alternator need battery power in order to charge battery.

SOURCE: New battery & new alternator, still not charging...

Take it to another auto parts store to test to verify.
If you put a voltmeter on the battery when the T+C was running, it should read 14-15V.
It could have a bad diode. If this is the case the alt. will be pumping out AC instead of DC. This is BAD. Batteries do not like this and the battery will fail because of it.
Be careful in those 'auto parts stores'. I have found that they employ alot of 'kids' who know little about how a car works. Try NAPA. They are much more knowledgeable and professional. But they cost alittle more.

SOURCE: Chrystler 2003 towwn and country won't run

Ignition switch is the most likely culprit.