Why would you have FOMO? Why is any particular gravitational wave important enough that you'd worry about missing it? I'm not trying to hassle you here, I'm genuinely perplexed by this attitude.
I used to work in a library and we all had a similar feeling about books. They were all valuable and to be preserved! Objectively, that's not practical. But that base irrational feeling is still useful and important.
Technically we've missed at least four billion years of gravitational wave events, so a week of shutdown for an upgrade isn't going to make a huge difference to that.
Yes, that's where the practicality comes in. But I'm sure there are people who have FOMO over all that data collection we missed over the last 14 billion years. And that's good! Maybe somebody will come up with something clever that is better than nothing. E.g., all the CMB work: https://en.wikipedia.org/wiki/Cosmic_microwave_background
My crude searching tells me there are ~3 supernovas in our galaxy every century. Miss one now and the next might wait for the next generation of astrophysicist.
Close by, interesting astronomical events are rare.
The last decent naked eye supernova was the crab nebula in 1054.
It would be a real shame to miss the next one in this galaxy.
Other "rare" (non-gravitational wave) events I can think of are: the Shoemaker Levy comet hitting Jupiter, the Carrington Event in 1859, Betelgeuse dramatically dimming (last year).
Last 'decent' naked eye supernova was surely Kepler's Supernova of 1604.
And the recent fading of Betelgeuse wasn't all that unusual for a fairly typical red supergiant pulsating star.
I replied to a sister comment similarly, but the one resource that we are severely limited by is time. There were events that were far more common in the early universe that we may never see now. Rare things could happen at any time.
The reality is that we can't observe 100% of the time for resource constraints and that the cost/benefit of upgrading is totally worth it in the long run - rationally speaking its the right move. I will just always wonder what we are missing out on that we might never have the opportunity to observe again - or maybe not in our lifetimes.
