I generally only have 1 running and have another to do an additional scan
avast/avira/ms essentials + malwarebytes
I have two active protections. Avast + Comodo IS and spybot and mbam for aditional scan. Never, i mean never had any issues.
Only issue's encountered were with old BitDefender's and Kaspersky's internet suites which i would not use if Eastern bunny brings them to me with new car (i would take the car