Bob wrote:

1) I keep my plane in a hangar at an airport more than 50
nm from the airport nearest my home. I decide to fly it
home for a week (1 hr), and tie it down. I fly locally for
that week (5 hrs), then back to my hangar airport (1 hr).
How much of that can I log as XC time usable for a rating?

All but the 5 hrs if you're worried about it. The rest of us log it
all. I log it ABC-ABD-ABC, on the same date.



2) I decide to take a long multi-day trip. Most days I fly
far more than 50 nm (25 hrs). Some days I fly "locally" to
see the sights and return to the same airport (10 hrs) that
is more than 50 nm from home. Some days I make only a
little progress and land less than 50 nm from the airport of
the previous day, but much farther than 50 nm from my hangar
airport (5hrs). How much of that can I log as XC time
usable for a rating?

To be legal as a cross country you have to land at an airport more than
50 miles away. Flying 75 miles out and then back without landing
doesn't count. It's a stupid rule but that's what it is.