As long as the drum stays sealed between dispensing, the oil will be OK.
If you are concerned about not enough usage, look into the 15 gallon drums of oil.
-- Travis McGee, main character in a book series by John D. McDonald
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.