I am trying to decide whether to have upper and lower eyelid surgery at one time or should I have them done separately?

Most patients elect to have both upper and lower eyelids done at once since they need to go the surgery process once rather than twice. 

It would be unusual to separate upper and lower eyelid surgery, unless that is your desire. Having both done concomitantly saves anesthesia, cost and two recovery periods. It is ultimately your decision, but it is not the norm to separate them.

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  For patients who are in good health, I recommend having upper and lower eyelid surgery performed together if you are an appropriate candidate for each.   Make sure you specifically look
at before and after pictures of real patients who have had this surgery
performed by your surgeon and evaluate their results.   The most
important aspect is to find a surgeon you are comfortable with. I recommend
that you seek consultation with a qualified board-certified plastic surgeon who
can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon