When do you get your shoes resoled?

....when they look and feel like shxt. I'd probably recraft them if there was a special occasion that I wanted to use them for.

I seriously wait until they start to develop a hole.  Really, I do. 

I only resole my shoes if they are from good brands, and I try to send them to the original factory to get it done. On the other hand, some generic GY-welted such as from Boggi or suitsupply will be straight to the bin once their life is over.

There are some experts here who will likely chime in as well and give a better explanation but I think there is a point where the sole gets soft and spongy and that is the time to resole. If you poke it with your finger it gives a bit at this point and no longer feels hard to the touch. If you wear all the way through you may damage more of the inside shoe bits.

That's a pretty good question. I believe you're referring to the midsole (the next layer). When you're into it, it's a more labor intensive process, I believe. Either way, when there is significant wear to the soles, it has an impact on the way you walk and your comfort (back included).

If you find the heel worn faster than the sole, just replace the heels. I won't always go back to the manufacturer, I've found a cobbler that does a great job with most repairs and maintenance.

I've certainly found that resoling shoes keeps me wearing them longer. Worn out soles makes me reach for another pair, so if I find myself skipping a pair because it's a bit worn, I will have it resoled.

Nah, you only screw up the cork a bit, and that gets replaced anyway. as long as you don't keep wearing them after the hole forms, you're fine.

Resole when there's a hole, or if the toe looks like it's going to eat into the welt (the next layer at the toe, which you don't want to damage). In which case toe taps are a good idea on the new sole.