Pretty much before streaming, ALL (American) tv had to fit into some concept of a time slot. This was done for a variety of reasons, most importantly for syndication purposes.

But to get around it, TV shows would do mulitipart episodes. A lot of To Be Continueds.

Twin Peaks was not immune to this. It’s long eps were 90 minutes each which, conveniently, divides up to 45 minutes per half for broadcast purposes.

Anyway, once you open that box, all bets are off. Star Trek DS9 ended its run with a literal 10-parter.