The "long duration 1st class ticket" is, after been issued to the customer, valid on the day until 4.00 am the next day.
A "long duration 1st class ticket" issued to the customer on 19 January 2017 is valid until 20 January 2017 at 4.00 am. It is not valid from and to a frontier point.
A "long duration 1st class ticket" is sold for €6.
If the passenger buys it on the train, the price is €7.
Use in 2nd class
A "long duration 1st class ticket" is also valid in 2nd class.
Of course you can buy a "long duration 1st class ticket" before your departure at train stations with ticket offices or ticket vending machines.
Train stations with ticket offices, ticket vending machines, Mobilitéitszentral (Mobility Centre).
In all CFL stations where tickets are sold.
CFL Call & Service Centre on 2489–2489
Find here the legal texts in French