I'd say it depends on many factors. If you immediately go out and get hammered and get very little sleep for a few days in a row, the changes will probably vanish much more quickly than if you being regularly applying some of the discipline you learned.
You can take a cold shower, or you can ride the momentum that the retreat gave you and keep the shower lukewarm. Sometimes it even gets hot and really nice feeling and you don't want to get out, but then after that kind of shower, even drying off feels good.
A retreat is a chance to get that pot of water to a boil. Once there, a little meditation each day will continue to boil the pot.
Without the focused immersion, a little heat each day might never boil the pot.
Note that this works for languages, physical skills (aikido) and many other complex tasks.