I do agree with @Howard Matthews (howiem) here. The timeline does behave sensibly:
You start with timeline being set 1 - 250.
You want the sequence to go from 300 to 600.
You start by entering 300 into start frame. Because Blender doesnt allow startframe to be larger than endframe, endframe is automatically changed to 300.
So you can happily continue to enter 600 into endframe.
That's workflow that makes sense to me :)
Should work like that everywhere.

Ok after @Luca Rood (LucaRood) talked with the artist in the studio this is not what we want. So the question is how urgent is this and are there other areas that should change.

Blender is indeed super inconsistent here:

• All simulations do accept start frame larger than end frame. (softbody, cloth, dynapaint, fluid etc.)
• Timeline works as expected.
• Seems it's really mainly the particles that have the bad behavior.

Hi. First time contributtor and absolute rookie on this kind of things. So, for a school project we had to pick and work on a couple of issues from here, and we chose this one for it seemed pretty simple and quick. Then we were instructed to try to submit it and while trying to find where to, we just now saw there is already a solution here, basically identical to ours. But as it is still set as open, here's ou solution anyway.

We basically did the same thing as @Danrae Pray (spockTheGray), on lines 825 and 842 but added/subtracted an instant to the adjusted value, simply so the animation always has a set time different from zero.

This is my first time contributing. I noticed we are not setting a clamp to this like we do for timeline (see "rna_scene.c" lines 881 and 891 for functions called "rna_Scene_end_frame_set" and "rna_Scene_start_frame_set").