The answer to your first question is - not often enough. In the past few years, I’ve mostly been playing against GnuGo, and making Opening / MidGame choices that lead the game away from life-or-death battles early in the game, so that might have shaped my thinking on this topic.
Having said that, I can certainly go back in my game history, and find human games where my opponent forced certain choices that made me either fight to save my corner, or invade their corner early in the game:
Specifically
MOVES 8-21 (I am White - fighting for the corner I just invaded)
MOVES 40-64 (Invading Black’s upper right and creating potential for a living shape)
MOVES 80-92 (Rather than running into the middle with my weak group, I realized I could use Black’s shortage of liberties along the edge for a big capture)
(Funny side note: I probably would have completely missed this opportunity if I hadn’t read THIS POST IN THE GO MEMES THREAD earlier that week! )
However, if you look at a different sequence, like
MOVES 101-116
This (IMHO) required a completely different set of Go skills (i.e. shape, cutting points, stages of the game, territory vs influence, giving your stones somewhere to run to, using direction of play, etc), and none of those were things that studying tsumego would have prepared me for.
But yeah, my “comfort zone” - if you will - is to mostly try and avoid situation where I need to worry about life-or-death edge battles, and where I rely on various other Go skills. Here’s an example I wrote up in my 19X19 FOR BEGINNERS: SHAPE article:
So yeah, while I acknowledge the importance of tsumego skills, it is also quite possible to play many games without necessarily ever running into situations that might require those skills.
Also, I remember a thread some time ago (6 months? 10 months?) where someone was using tsumego sites exclusively to learn Go, and was being told that they were solving tsumego problems equivalent to a 12-15kyu level. However, when they (a 25 kyu player on OGS at the time) tried playing higher ranked players, they routinely lost - and they were trying to figure out why the skill level that the tsumego site gave them wasn’t reflected when they played 19x19 games against human opponents.
I made a similar comment at that time, and I stand by it. The game of Go includes many skills that studying tsumego will not teach you, and to over-focus on those set of skills at the expense of others may lead to confusion down the road. This is why I urge beginners to generalize rather than specialize early on.
Your mileage may vary, some cars not for use with some sets, contents may settle during shipping, void where prohibited.