"skin-to-skin" for traditional OHS, meaning the time from incision to time of closer, can certainly take a few hours as there is a lot going on in-between. e.g. chest is cracked open, hook-up to heart-lung machine, heart is stopped, cutting to remove old valve, sizing and stitching of new valve, TEE/imaging, disconnecting from heart lung and restarting heart. Tack-on a few more hours if they are cutting through scar tissue if this is not your first OHS.
There is also the prep time needed before the first incision is made. These things would include insertion of IV, various tubes and catheters, and administering meds and anesthesia.
The day will go fast/seem like a blur for the patient but will be a long one for those waiting. Although you may not be fully awake yet, I would say for those waiting to expect to see you in ICU 6 to 8 hours after they see you wheeled back for your surgery. You should inquire how/if COVID protocol will impact visitation.