FBM Automated handling time

Can someone help me understand the OTDR and late shipment rate metrics? I make custom products and have set my handling times to give me ample time to make and ship the products. In anticipation of the forced move to automated handling time coming soon, I’ve started to ship closer to the expected ship date. I’ve noticed that if I ship on the ship by date, it doesn’t meet the deliver by date with USPS and bumps me to the higher UPS rates. Will my automated handling time continue to get shorter and shorter as I need to beat the ship by date to get USPS rates?