The amount of time you are going to be able to handle the joeys is going to depend on the
bond you have with the parents. If you holding the joeys is causing undue stress to the parents, then you may need to slow down and wait until the parents are more comfortable with you. Every few days, you can gradually increase the amount of time spent. Remember that a newly OOP joey nurses quite often and should not be kept from the mom for a long period of time. The following chart is a general guideline that was created by Suz Enyedy with Suz' Sugar Gliders:
Day 1 - 7...5 minutes, in sight of parents
Day 8 - 14...7-10 minutes, in sight of parents
Day 15-21...10-15 minutes, near parents
Day 22-28...15-20 minutes
Day 29-35...20-25 minutes
Day 36-42...25-30 minutes
Day 43-49...30-45 minutes
Day 50 - 56...45-60 minutes
Day 57 - 63...up to 3 hours
Day 64 + ...joey should be fully weaned