We have a community with a lot of what I call “drive by” users. They show up with questions about our software, get their answers and happily (and quietly!) go away.
Even the most active users, who come back again and again to help others have only reached Trust Level 2:
That makes me wonder if we should tune the trust level requirements.
I’m guessing the defaults are set for a “let’s discuss sports” type community…?
Does anyone have any experience with this?
The Default Trust Levels are only recommendation and should be adjust per community needs.
In saying that, there are other options you could also consider.
Like, rewarding the loyal users and adding them to a group which keep them on TL3. Another way is to lock the specific user’s TL and adding them manually to TL3.
The final decision needs to be made by the CM.
Good Luck 
In a past life I ran a community using discourse where some people got competitive about reaching trust level 3, and frustrated when they did not reach it or retain it once they got it by continuing to meet the requirements. I tried a few things to assuage them but eventually just hid the trust levels so they were no longer distracted by them.
Personally, I would recommend creating more groups and badges to reward your users, and leave the trust levels as they are as long as things are working well for you otherwise. The trust level requirements are tuned already to protect and serve your community, so you don’t have to do too much manual intervention to deal with spammers etc.
Trust Level 3 provides near moderator level capabilities, so you don’t really want to have too many people automatically entering it without for sure having demonstrated that they are committed and trusted members of the community.
In case you have not already, see Understanding Discourse Trust Levels | Blog for more on how trust levels work.