You are not wasting your libraries and universities. Increasing your science rate can get an occasional science in one turn. This is especially true if you build more cities and develop them. Grow the ones you have with President's Day. By sending out high-value caravans, it is even possible to get more than one discovery in a turn (caravans alone can only get you one).
To answer your implied question:
Some bulbs will always be lost. If you need 20 more bulbs to make a discovery and your next city generates 60, the extra 40 bulbs will be lost. This is true for every discovery you make. Unless a city generates the exact number of bulbs you need at the time it comes up in the city check (not worth trying to make this happen IMO), any surplus bulbs it generates are lost.
Even worse, if the city that normally would make a discovery completes work on a building or unit, it may (over)fill the research box with bulbs, but you won't get the discovery. The discovery will pass to the next city that is not completing production of something.
