When I was a youth, I didn't qualify for Interrail, coming from North America. It was Eurail for me. I needed three months worth of rail pass. As it happened, there was a three-month first class Eurail pass, but the second-class one came only in one-month and two-month versions. It ended up being only $60 more for a three-month first class pass than for a two-month and a one-month second class pass. I figured it was worth $20/month to upgrade my pass to first-class. This was great for night trains, when the first class seating compartments were pretty much empty (real first-class passengers preferring beds or couchettes). But you could pull the seats together across the compartment to make the compartment into one big bed. I took a lot of night trains. Free accommodations to take me from city to city whenever the hostel was full.
When I was planning my European trip with my daughter for the summer of 2020, almost 40 years later, I looked for some night trains to take us from city to city, but discovered that they are more or less a thing of the past and are few and far between now.