I won't have a pet we can't insure now - we have two dogs insured and one who isn't due to his age. Going forward, we won't get another dog until we can afford decent (ie pet plan) insurance.
We have two credit cards, both with no debt at all on them, so in theory I could spend around 20K. I am unlikely to do so though... we also have a savings account and what I would spend on insurance for the oldiewonk gets put into there, however as I am on UC there is only so much I am allowed to save before that then gets deducted from my income (not that I disagree with this!) so as a long term plan for future pets, thats not an option.
So yes, I would go into debt, but not beyond my means to repay it comfortably.
Yes I would spend thousands if necessary.
No I would not spend thousands (or anything in fact) to prolong an animals life where that is for my benefit rather than theirs/ not in their best interests.
So using the old chap as an example - I might get him a dental and a lump removal, I might not, he is 16 - depends on what my (very trusted) vet says - a few days of feeling a bit rough with a clear benefit, thats ok. But weeks and weeks of feeling awful with no major benefit... that wouldn't be ok, we'd just let him go.
Will I prioritise the dog over me... not over my health, no but I am currently not replacing the dryer that makes a fuckawful squealing noise, because I am hopefully getting the old fart a dental!
I'll always put pets before things where the things are 'nice to have but not vital'.