I figure that it's mostly personal preference, so experiment and see what works best for you. I imagine that most people avoid double shifts most of the time and stick with one chainring until forced to switch it. The only time I'll do a double shift is a long stretch where I'll be staying in one gear and want to fine tune cadence. Going up or down hill you probably won't stay in one gear long enough to bother double shifting. Depends on your gear ratios of course and the size of the jumps between and how narrowly you want to maintain a certain cadence. I'll often spin up to 120 rpm before bothering to upshift, but I'll downshift if I'm below 80 in the saddle.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72