I am just adding in perspective and breaking up the generalization that you made. As well as pointing out that May to September is longer than 1 month (longer than 2 months as well). No need to get snippy.
You may be very well right that the longer time of knowing someone would be better for the OP, but we don't know all of the details. That is why I worded it the way I did. Longer time could be better if the relationship is strong, but you can still have a strong relationship with someone you have known for only 5 months and a weak or ok relationship with someone you have known for years. That is now up to the OP to decide where their personal relationships with each potential eLOR falls into place.
I applied a few years ago now and if I remember correctly, once you added the person to the eLOR system they were sent an email with how to log in. Once they logged in and started working, you could no longer delete. I don't know if that has changed or not since I applied. This is a good question to call up VMCAS and get the word straight from them.