I had the same issue, what I was told when they did the R&R the take out a valve that lets the fluid bleed back down. This is to have better flow for better cooling. Some shift kit's have it done that way. I know have a full DTT with everything and it does not do it. One thing that will make it pump up fast is to start the truck and put it in neutral. This will cut the time down in have. .
Look at it this way, now your truck will run a moment before you need/can leave. I think that's what the issue is.