I suppose it's down to what you've got used to listening to. An album is designed to be a good listening experence, & at around 30mins. (for older LP's) doesn't outstay its welcome. There's no hard & fast rule for me, once I'd heard the original tracks for Ben-Hur & The Great Escape, I lost all interest in the original albums, but for Our Man Flint & In Like Flint I prefer the album re-recordings to the original tracks (hint Mr. Intrada

). It's best when a release has both, but as the album & original are usually owned by different companies by now, it doesn't happen very often.