It doesn't make sense that the train trip the Ricardos and the Mertzes embark should take 11 hours. In last week's episode they were in Florence and now they are heading to Rome which is approximately a 3 hour car ride away.
Ricky tells Lucy that they're in Rome for 10 days. Lucy tells Ethel they've been in Italy for a week. However, before the trip began it was only for 3 weeks of one-night stands.