It'll remain till you activate it for the next sector. You can store it as previous
suggested so as to use the SEC FLT PLN but dunno why - there's nothing you
can't do already on the PRI PLN or do an insert on the RAD NAV if ATC decide
to suddenly change yer runway. The missed appch can still be done raw data
like we used to do in real aeroplanes.
Only exception is bloody China (specifically Beijing) where there are a dozen
STARS for each of the 3 runways and ATC never tell you to use the same one
you used yesterday. Best to put the most likeliest other STAR in the SEC PLN
in case, as its not till your on App freq that the buggers will advise the STAR.
The SEC FLT PLN though is very handy for enroute use such as redispatch and
PNR (incl PNR EO) calculation. If you want to set up the next sector do so on
receipt of the wx about 1 hr prior to arr so as to determine RNY and perf figs.