Brakes left set to Park or Released?
Can't remember for sure about the B707, however the B747 Classic
"Parking Checklist" calls for, in respect to Parking Brake;
"Parking Brake"...................................................... .. Set
(Check that the Parking Brake and Anti-Skid Hyd lights are illuminated.)
"Shutdown Checklist" says;
"Parking Brake"...................................................... ...As Required
(Release Brakes if not required)
That is what Boeing has to say about it, what individual companies do is their call. Personally, if the aircraft is properly chocked with appropriate chocks I can't see any real need for leaving the brakes applied for extended periods.
Thanks Muduckace, as I said, I did not doubt your post. I guess some people just go for an extra bit of "insurance", especially if the area is prone to very high velocity winds. I think the point on increased pressure due thermal expansion raised by stevef is valid.