Occasional travellers tend to dismiss rail subscriptions as something only regular commuters need. The off-peak discount card is where that assumption gets tested, since the break-even point and the specific hours covered determine whether it suits a given travel pattern at all.
At €6.35 a month, it pays for itself faster than people assume. Dal Voordeel gives you 40% off during daluren (off-peak hours) — weekdays from 9am to 4pm and after 6:30pm, plus the entire weekend from Friday evening to Monday morning, and public holidays — and the math works out so that a single round trip of around €16 at that discount already covers the monthly fee. That means it's worth it for anyone who takes even one or two off-peak trips a month, not just regular travelers; a commuter who mostly rides during rush hour won't see much benefit since the discount doesn't apply then, and should look at a different NS Flex product instead. The only real catch is remembering to check in with the linked OV-chipkaart or OVpay every time, since the discount applies automatically at check-in rather than being baked into a fixed fare.