when does a "remain clear" instruction end?

Steven P. McNicoll wrote:

"Michael Houghton" wrote in message
...
Consider the following scenario.

You take off outside the Class C and would like to transit it. You are
instructed to remain clear. You circumnavigate it, reach your destination,
and return without landing. You again approach the Class C with the
desire to transit rather than go around. You call up ATC again and they
reply with your tail number but no instructions. Can you go in or not?



You can go in.



I'm positing on the order of an hour or more elapsing between the two
attempts to transit.



Right. It's a different flight, unrelated to the first.

What makes it a "different flight"? He didn't land in between, just flew
around for about an hour and came back. Would flying around for half an
hour and then returning be sufficient to make it a "different flight" and
thereby cancel the effects of the 'remain clear' instruction? How about 15
minutes? Doing a 360?