The 1970 Palmer is one of my favourite wines from the vintage, along
with Latour and Montrose.

Unfortunately I have noted a tendency for it starting to break up over
the last few years unless cellared impeccably. It would be a bit
dodgy buying it now unless you were very careful about provenance.
Bottles properly cellared are, as you noted, good to excellent. It
will not get any better, so saving it long term isn't likely to be a
happy experience anyway.