One and two no longer apply to me I guess. So.. for the other two questions?
3. I think the most successful games I've been lucky enough to be a part of were that because of a mix of balance and luck (Luck largely because Real Life happens). I've been fortunate to have some great GMs and co-players who know how to keep the action flowing by example with openings for everyone to chime in ICly or what not. Speaking for myself personally, I react well to a sense of achievement, not for just MY character, but for the group. A sense that the setting is BETTER for the characters having been there.
4. I've had some great game masters who got HAMMERED by Real life just as they were getting a game going. Medical problems with them or their family members, sudden moves, legal woes, job demands increased without warning. If it happens to the GM, or enough players, it can have an effect. APs can be really tricky for this reason. They take a long time, so the odds are greater for player or even GM loss. There's also a matter of fun not being had. I've seen some Game masters and player groups that had different expectations but didn't realize it until it was too late. It stopped being fun for the GM or players, and what should be a game became nothing but a chore. It has to be fun for the GM or what's the point? And I quite understand when a GM or player has to say "Sorry, this isn't working for me " and withdraws
Sorry for the wall o text