N2L - I agree with the others, it's a hard question to answer.
In our case, my answer now is different to what it was before we were blessed with DD. DH and I had a discussion about what we would do if we didn't have kids, right before the TF that we got pg with DD from. We said we would sell our large family-friendly house in the burbs and move to an awesome city apartment, and do lots of overseas travel. In fact, if that TF hadn't worked we were going to take 15K from our mortgage and blow it on a 3 week euro trip over NYE etc. We had everything planned out, down to the flights we would book and hotels etc as pretty much as soon as we got our BT result we needed to book the trip. And we got a BFP. So, no trip. I think I had this mentality of let's make these plans and then hopefully we will have to cancel them.
Anyway, I digress. For us we were lucky that the money wasn't (at that stage) an issue - not that we're loaded but we were able to afford the 2 stim cycles we did and the transfers. Mind you it costs more these days. But I really really struggled with the stim cycles, I have a blood clotting disorder which meant I also needed clexane shots daily, which means you bruise more easily, and as someone who already bruised easily - well, my poor body got a thrashing. I also found it hard because my lining took ages to prep, I ended up on estrogen patches (on my butt!) as well as crinone and all the trimmings ha ha. Every time I had a scan it wasn't good, taking forever and infact during the stims I never got great hauls of eggs - 1st cycle only got 2 embies, 2nd cycle we got 7 embies. I'm not sure at what point we would have decided to stop, but I'm one of those people who truly believes if something was meant to be, then it's meant to be. So maybe we would have stopped after a few years (more than it took, itms)...
This time around I am not filled with the desperation I was the first time. Also we started with 6 frosties so rather than stims it's been easier on my body. Still very tough on the mind of course. DH and I haven't discussed how long we will try this time, perhaps we both naively assume it will work 'soon' because it worked 'before'. But, with 5 frosties now left, maybe if they run out and we have to do a stim... well I could do one stim for sure, maybe 2, but beyond that i don't know.
Everyone is different, in different situations etc and there's so many factors to weight in.