I’ve had the radiator out the car whilst doing another job and although the last time i took it off was only about a year ago the top and bottom hoses had stuck really hard onto their pipes and took a fair bit of persuasion to be released.
I had read in an article that red rubber grease is the best stuff to use on rubber as oil based products will attack the rubber. It’s also good to wipe around door and boot rubbers to prevent them sticking closed in freezing conditions. It’s also recommended for use on lubricating brake mechanisms.
I’ll see how effective it is next time I take the rad out ……… hopefully not for a while.