Changes

Every bus has a machine to punch holes into the ticket which are shaped in a certain pattern (saying - there's no time limit on the tickets). People often leave there used tickets on the seat or drop it on the floor, so just take one and be happy. Alternatively always have a fresh ticket with you and punch it as soon as you see the controllers from the distance (they have a separate minibus and are usually 5 or more in shiny uniforms - easy to spot) - that said, it rarely happens that there are single controllers or conductors teams consisting of two people. You could technically spot them as well though. (Marshrutkas Minibuses aren't so common in Vilnius and usually more expensive than the buses/trolleys.)