What is an alternative (more positive) analogy to "beating a dead horse"?

I'm looking for an analogy for my repeated attempts to revive interest in a project. The phrase beating a dead horse almost fits the bill, but a dead horse refers to a subject that is no longer relevant or useful, and this project is both relevant and useful, it's just considered a low priority.

Without giving the subject a negative label, is there an analogy I can use to express my persistence and frustration?

Dubs, it sounds like you still believe in the project and are trying to breathe-life back into your interest group. I agree the 'beating a dead horse' phrase does not convey your feeling, and I wouldn't think the analogous terms mentioned would either. I can't think of something exactly, but I would say something like: 1) 'at the risk of sounding like a nag'... 2) there is an expression about driving a nail into a wall...'I hate to drive this nail into the wall, but can we arrange to meet again...'. You may not like this latter phrase because it implies over doing something. Good luck.

Stop beating banging your head against a wall, if you wish to avoid unsavoury animal-cruelty based clichés.

I think you were almost there since the usual form of the cliché in your question is flogging a dead horse.

Alternatively, you may have tired of trying to push water uphill.

Perhaps the task is Sisyphean?

Actually a good "analogy for [your] repeated attempts to revive interest in a project" is like trying to write a grammatical and accurate answer in English.stackexchange.com".

Perhaps you could borrow a page (line) out of the forensics/criminology phrasebook and call your project a "cold case".

Cold Case
A crime that has remained unsolved for a long period of time, has no new evidence, and has been deemed a low priority by its original investigating agency or department.

That is to say, your project has been put on hold indefinitely but isn't (at least as far as you're concerned) quite dead yet.

Of course that phrase doesn't directly describe your efforts to "revive" the cold case (so take this answer with a grain of salt), but it indirectly suggests that someone passionate about it with "evidence" of its continued or renewed relevance could well do so. And you could use this analogy to expand the phrase to something like:

It's like trying to revive a cold case.

The implied frustration involved with this process should be evident to most readers who know what a cold case is.