However, as to the length of the symphonies, I'd be willing to be the majority of symphonies are under 30 minutes. I don't think any symphony reached 40+ minutes in length until the Eroica.
Out of the 26 symphonies mentioned, only Beethoven 1&2 were written before Eroica.
All four of the Brahms symphonies are 45-60 minutes.
Tchaikovsky 4-6 are all 45 minutes or longer, not sure about 1-3 but I'd be willing to bet they're well over 30 minutes.
Some of the Sibelius symphonies are pretty obscure, but the 2 well known ones are both pushing an hour (and given Sibelius' style I'd be surprised if any of the others are less than 45)
The only ones that are considerably less than 40 minutes are some of the Beethoven...1 and 2 for sure, 7 is shortish...3,6, and 9 are all big, long works...have to admit I'm not that familiar with 4 or 8.