Only during repetitive figures. However, as a composer, you have to develop your use of rests. If everybody is playing all the time, players have nothing to anticipate.
I struggled with the middle range instruments for a long time. I used to give violas nothing but running 8th notes in my trios and quartets. I got over that. You learn to divide the action between parts so you can have a repetitive figure shared around the orchestra.
Also, I just write interesting material for most of the instruments in the orchestra. If players hear something interesting going on, it makes them want to play harmony. That is what I would expect. I'm a violist and second violinist in my school group by request.
So yeah, I used to worry about boring the players. Now I just focus on making sure my music is just right. My music has the notes I require, not more nor less.
"Maestro"