The great thing about a listening session - of whatever basic type, say classical, jazz or even pop - is that it does not have to be concert length.
Sometimes I have a piece of music running round in my head at work, so after supper, I play that piece. It may be less than ten minutes long, and may even be all the music I play that day.
Another day I may construct an imaginary concert from one conductor and orchestra from recordings made in a reasonably contemporary period, so as to get a sense of continuing style through all the music.
Another day I may start with a solo piano piece, and then go onto a piano concerto and then a symphony.
In other words, though there is shape to my listening there is no fixed pattern or length.
Sometimes I might even listen to four very large [in length] pieces, by varying instruments or orchestras, and that would never be done in a concert.
I am sure that all you need do is listen to music you love ...
ATB from George