There are actually two types of event serialization: serialized per visit, and serialized via event ID. Both can be activated in the admin console under report suite settings.
Serialized per visit means that only the first instance of an event is counted per visit. event1 can fire on every page, but it will only be recorded once with this setting enabled.
Serialized per eventID uses the logic you stated: s.events="event1:12345" means that if Adobe Analytics ever sees another event1:12345 it will be tossed out. As long as the string in s.events comes out in the right syntax, you can use whatever value you'd like.