You may think it noble to "only take donations" just to pay the hosting cost, etc. but providing people support is a completely different thing. People are stupid, needy and inconsiderate of your time, feelings and experience.
If you don't want to run ads, great! But your time should be compensated fairly as well. You should be charging businesses for things, with a substantial cost for substantial work. Charging a business is not the same as charging an end user and you should not be averse to doing so.
As a user, free or paid, it'd give me a lot more faith in this living past tomorrow.
And the risk of this project is largely mitigated by offering the full repo as open-source, so you can always self host this if needed.
The latter should be easier to manage with more predictable traffic, while giving you more leeway to deal with abuse on the free servers if it ever becomes an issue.
(a) They're making millions, you deserve a cut of that.
(b) If making money makes you more likely to be around in 10 years, that's attractive to businesses. Nobody knows when your donations might suddenly dry up.
I honestly believe this project can cover $175 per month eventually.
Of course there is the countless hours which went and which can possibly go into this, but to cover the hosting is still meaningful.
Let's say 1 year from now your day job gets toxic and you have to work 18 hours a day just to pay your rent and expenses. Are you still going to maintain this?
What if the economy goes to shit and you have trouble scraping that $175/month? How long are you going to pay $175/month for something that isn't making money?
What if, instead, this became a part-time job of yours?
If I was a commercial user of your product, some assurance that your random personal situations aren't going to affect the product stability for a long time would be a good thing.