My main catalogue has 175,000 images in and yet the actual Lightroom Catalogue file is only 2.2Gb. The answer is just to back that up and your risk is minimised. The Preview data file for the same catalogue is 82Gb - which I also back-up, but it is not a critical loss if that goes. The Catalogue can rebuild the preview data if necessary.
Just to make sure everyone understands:
I have no problem with LR at all - I'm fine with it just the way it is. No product of any kind is perfect (in spite of the over use of the word perfect, but that's a whole different subject not related to photography). Anyone expecting perfection is bordering on insanity - and I'm not saying which side.
The problem with the (vain) attempt to make LR satisfy everyone is that it starts to look like the racehorse designed by a committee. What's worse is that with software it soon becomes bloatware and effectively executes itself (as in dead).
There is a simple solution for anyone that doesn't like the features in a product and isn't complaining.
The person on the other forum that suggested that it could take thousands of hours of work to redo lost edits may have a point - or perhaps his collection could use a bit of thinning down. However most of us are reluctant to throw anything away - we humans do collect a certain amount of junk. I've decided to get rid of the chaff - a few months ago I had about 40,000 images - I'm down to about 23,000 now and there will be more "reassessment".
I'm wondering out loud because I simply don't know: If a wedding photog takes a few thousand images for one wedding, and the couple gets say, the best five hundred, what happens to the out-takes? Do you keep them? If the people that buy the good ones don't get the bad ones, why keep them? Can you use them for someone else?