I don't use them at all when I have kids that still put things or hands in the mouth since that means it all transfers to the toys, then gets stirred up so all the germs from the mouth are now buried in the bin to grow. Not a fan of sensory bins with under 3 at all due to the dangers of the items normally used. I don't have anything out for the older kids that I can't turn my back on while my youngest ones are in the room. I have some special toys that come out only during infant naptime which is another reason for giving the infants/toddlers a short respite time in the morning even if it is a playpen or playyard if they don't sleep anymore. I have tried putting the older kids up to the table with smaller items and then keeping the little ones busy in another area but I found mostly I had the older kids wanting to join us too just because that is where my attention was being given so it defeats the purpose. What I won't do is make an infant/toddler sit in their highchair so the older ones can do art, small toys etc since that isn't fair to the infant/toddler who has their own learning they should be doing.