Thanks for clarifying that for me Mark. I had forgotten about the pins 'floating' when in input mode.
I have been pin-powering the RTC's on my loggers for a very long time now without apparent ill effects, but in that case its soldered directly to the IC leg, with no capacitors to worry about.
For my analog sensors, I always try to use higher value resistances (like a 100k thermistor instead of a 10k thermistor) so that those pin voltage drop errors are smaller by comparison.