Currently, the way donation goals work isn't very average streamer friendly. You can only set one goal, and it must be within a time limit.
This is good for say, one-off fundraising nights, but being required to set an end point to a donation goal can in some cases defeat the point of the goal.
Say you're using your goal to get a new Microphone - the goal doesn't need an ending. It will end, theoretically, when you can afford the microphone. Especially if you're a small streamer, sometimes your goals will last for months at a time, and it can be annoying putting the time limit to an extreme date, say hundreds into the future, in order to hold the goal. I mentioned this problem to a Streamlabs staff once, and they blew me off by implying that donation goals usually have an ending. And while he's true, it's more rare that people go "I will end this donation goal when I hit a certain time limit". Most people I see end the goal, or at least try to, when they actually hit the goal.
Then to the second part of this - the fact you can only set one donation goal. This again falls under the problem of not being streamer friendly. Sometimes you want to keep a long term goal, but a short term goal might come up - I know many streamers who end up having medical problems where they quickly need to fund-raise for the medical bills, and I'm sure many of us know someone like that too. It's unproductive to have to get rid of your long term old goal, (say a microphone), then replace it with a short-term goal like medical bills or other fundraising, then have to re-make the previous donation goals.
Both of those sure, are small problems - minor inconveniences. But they add up with a lot of hassle. I think if we simply have an infinite duration option, and the ability to set multiple goals, perhaps set an active goal too, managing goals on Twitch would go from painful to easy.
(I posted something similar to this months back, but it wasn't the full suggestion so I've put them both into one, now)