According to the Wikipedia page for "Symphony", during the 17th century, the symphony had a fairly set structure:
The four-movement form that emerged from this evolution was as follows:
- an opening sonata or allegro
- a slow movement, such as adagio
- a minuet or scherzo with trio
- an allegro, rondo, or sonata
While it may not completely fit the above structure, Mahler's Symphony No. 3 often runs 90 to 100 minutes. So "symphony" is a candidate answer. Operas often run longer than 90 to 100 minutes, but might not have a clearly set structure.
Opera Seria is an Italian form of opera, also with a fairly set structure. From the Wikipedia page:
Opera seria built upon the conventions of the High Baroque era by developing and exploiting the da capo aria, with its A-B-A form. The first section presented a theme, the second a complementary one, and the third a repeat of the first with ornamentation and elaboration of the music by the singer. As the genre developed and arias grew longer, a typical opera seria would contain not more than thirty musical movements.
A typical opera would start with an instrumental overture of three movements (fast-slow-fast) and then a series of recitatives containing dialogue interspersed with arias expressing the emotions of the character, this pattern only broken by the occasional duet for the leading amatory couple. The recitative was typically secco: that is, accompanied only by continuo (harpsichord and cello, sometimes supported by further bass instruments). At moments of especially violent passion secco was replaced by stromentato recitative, where the singer was accompanied by the entire body of strings. After an aria was sung, accompanied by strings and oboe (and sometimes with horns or flutes), the character usually exited the stage, encouraging the audience to applaud. This continued for three acts before concluding with an upbeat chorus, to celebrate the jubilant climax.