Do I need a maintenance or field service kit for an MSR liquid-fuel stove?

Over time, yes. Liquid-fuel stoves rely on O-rings, a fuel pump, and a fuel line that can clog or wear. MSR sells dedicated O-ring kits, replacement fuel pumps, and expedition field service kits, all of which carry strong verified-purchase ratings, and owners of these stoves widely recommend keeping spares for long trips.