It could be today or it could take a month or two... no one can say for sure.
RFE is a purely random pick, 1 in every 5 gets a RFE.
The probability of getting a RFE gets lower as each day passes without you getting a RFE. keep track of RFE data on rupnet, as the % RFE'd approaches 20, your risk diminishes.
RFE is not a bad thing if you have a job and all papers are in order, its the next best thing to an approval.
Try to take it easy...... its a process and it takes time.