Is (was) an LP by definition 33 1/3 rpm?
You could fit a shitload more on a 16 RPM disk. These were not used for high-fidelity sound though.
Other factors: later technologies enabled them to make the vinyl peaks between the valleys narrower. That meant more info per side. That tended to coincide with a flexier disk. The really old disks were hard and cracked quite easily on impact; the disks from the late 40s thru mid 60s were mildly flexible, less fragile, and seemed able to contain more info as need be. From mid to late 60s onward, the disks got thinner, flexier, far less fragile, and extra tracks were sometimes added to vintage albums as they could now accomodate more info on a record. By the end of the vinyl album era, you could hold them in your hand by the edges, press inwards gently, and see it warp in your hand to a very impressive bow.
<damn fuckers still scratched at the slightest provocation though. I hated vinyl>
I am going to guess that they peaked around 60-65 minutes per 33.3 RPM disk. Beyond that you’d get a double LP.
45 RPM singles I have no idea about. Never owned more than perhaps 10, lifetime total.
ETA: Cite re: more space over time. Harry Belafonte To Wish You A Merry Christmas. a classic LP on re-release included a new track “Mary’s Boy Child”, without nuking any of the other tracks to make room for it.