My DD is always spilling drinks in the lounge as she takes one or two sips then leaves it to one side. For that reason during the day in the lounge she has a sports bottle, but meal times etc she has a normal glass. She is 3.9
Ds never spills a drink and always uses a normal cup he is 2.6
I think you keep using lidded beakers (or at least those sports bottle type things) for ages. DD1 (3.7) always uses open cups at home, but takes sports bottle to nursery with her drink in (how else could I put it in her snack bag?) or if we're out and about all day. DD2 (19 months) always uses an open cup when sitting at the table for mealtimes, but beaker otherwise. I also give both of them a lidded beaker of milk first thing in the morning as they come into bed with me in the morning to drink their milk. So long as you regularly use open cups so that they are used to and happy with using open cups I don't think it matters to have a beaker around for occasional use when it's convenient (you won't need to keep a drawer full though - just one or two!).