Pat, There are quite a few people on here who have had work done on more than one valve at a time and have been fine. I had my tricuspid valve replaced, an asd patched and a maze procedure done all at once. I think my surgery took around 7 hours or so (can't really remember) and I did fine. The most important thing is to make sure that you are using a surgeon who has a lot of experience fixing the things you need to have fixed. Also, by saying you have been cleared for Robotic, are you saying that it is going to be minimally invasive? Personally, if I were having that much done, I would want a full sternotomy so that the surgeon had full access to everything, but that's just me.
I know this is a very trying time. We are here to support you in anyway. Ask any questions you may have.
Best of luck to you,
Kimmie