Each sanctioning body is different, but I can give you the "skinny" on NSA since that seems to be what you're asking for based on your first post.
There was only one alternate state and it was announce VERY late - it was the Spano Dome tournament in February. If you attended that, and you qualify (or have already qualified) for NSA nationals, then you do not have to go to NSA states at Tealtown to maintain your berth.
In order to qualify for NSA nationals, it is rather easy. Not to knock anyone who goes to NSA nationals as we have teams that do and I'm sure my team will go again at some point, but it's extremely watered down IMO. If you attend enough tournaments, you will eventually get a berth for NSA nationals. Why? Because initially you have to place in first or second in most tournaments to get a berth (one berth for every four teams entered for NSA) - but after that - if the first two teams have already qualified, the berths pass down. So, by the end of summer at the NSA national qualifiers, you have last place teams in the tournaments being awarded berths to Nationals.
Once you qualify you then have to attend states to "keep" your berth.
Anyway, hope that helps.
Marie