In the AU scene, there have been a lot of low "division 1" (not necessarily invite level, but it's our top skill division so whatever) teams that have stuck it out for quite a while.
Bear in mind we're a different scene and as such skill divisions etc will be different to NA (no shit).
vivid reprisal (a team comprised mostly of admins, funnily enough I guess) have been together for 2, nearly 3 years and have worked their way from Division 3 (mid open I guess) all the way to a low/mid division 1 team (so low-mid IM I guess). For the most part, there have been a few members that have been there consistently season to season, but there are some new faces. The reason why some members left in the past was not necessarily the teams performance, but for personal reasons for the most part (and from my knowledge, occurred at the END of the season).
Sure in Australia we don't have the "structure" of ESEA, let alone a LAN as prestigious as ESEA for Division 1 finals etc, but as Ruwin said: people that have gotten into the top skill division through hard work and mettle have been proud of their accomplishment and quite a few of the teams have stuck it out for continuous seasons despite their "sub-par" performance. I'm not trying to compare the skill of Division 1 to Invite because for the most part the skill differences are pretty obvious. What I am trying to do is basically further reiterate Ruwin's previous posts.
I think people just need to stop being bitches at their teams performance and stick it out. If you stick it out with your team through thick and thin, THAT is where you start seeing yourselves becoming better.
TL;DR - don't leave your team (especially mid-season for the matter) unless it is actually important. Stop being a bitch.
On another note - Ozfortress has the ongoing "Ozfortress League" where teams that want to get into OWL (the main league) must prove their worth (ie, not disband in a week) before they even get considered for OWL. Maybe a similar idea is needed for ESEA?
EDIT: I guess it helps that the AU leagues are free - but I think my points are still relevant for the most part.