I think it depends on the hospital. When I did with RH, I came a couple of times for blood test and scans. They are done to check for lining, size of follicles and the LH surge. My dr also told me to check the OPK. I was kiasu so I checked every few hours. Once the test line is darker than the control line, then I call the clinic and they will ask me come down for a scan. The day for the transfer will be your ovulation + the age of your embryo was frozen. When I did with NUH, from day 9 or 10, I had to come daily for scan and blood test. Dr didn't ask me to test using OPK. Super tiring and was such a bummer when the surge didn't happen and my egg started to shrink. Had to abort that cycle and ended up having to pay about 1k still.