Good day!
At least for responses, I have not been able to sense a time limit either. I've been interrupted while composing and had to be away from the computer for an hour of more. Sometimes I return to find the post still in an editable, In-progress status. Other times it has timed out. There is no pattern I can sniff out.
Rather than set a timer, try what I do. When working on a longer responses, like the ones that require research or making illustrations, I copy what I've written if I need to be away for a bit. You can leave it in the Clipboard but I usually paste it into TexEdit.
There is also the option of doiing all composing in a text editor. Believe me, most text editors have better spell-checking than the forums' text entry boxes! You may still need to insert links and images using the forums' text entry box, Depending on the source, pasting links and images from a text editor may not always work as planned.
And, by the way, welcome! We love to see people wanting to help. Here are tips I like to give new users like you with an attitude of helping:
The effective way to help here:
—Bookmark this forum site map: https://discussions.apple.com/productsitemap.jspa
—Choose topic areas where you feel you can best help.
—Use the site map’ topic links to go directly to those topics.
—Work the first few pages with the newest posts.
That gives posters the most current information, and they can recognize your contributions with an upvote.
Coming from a search engine is not very effective as it leads to too many old, locked threads.
Allan