If a doctor removes too much fat with upper bleph...will that fat grow again? What happens to the eye with age... skin droops?

It would be very helpful to see some before and after pictures to answer this question.  There is fat in the lids that extends back behind the eye.  With age, some of this fat may move forward.  So after your fat removal, you may notice some fullness again after several years.  In the meantime, you can fill under the bone with some hyaluronic acid filler, or fat.  If you have some excess skin that can be excised.  It may make the lid appear deeper however.   

During an upper eyelid blepharoplasty if too much fat is removed the fat does not grow back. The future result as one ages cannot be predicted.

I usually try to remove little, if any fat, from the upper eyelids to avoid a hollow or skeletonized upper eyelid. The fat will not grow back after removal but can be replaced with either fat transfer or dermal fillers if you have developed a hollow upper eyelid. Replacement of that volume can be very, very tricky so please seek a consultation with a plastic surgeon experienced in volume/ fat replacement in the upper eyelid. I hope this information is helpful for you.Stephen Weber MD, FACSDenver Facial Plastic Surgeon

Fat that is removed in upper eyelid surgery does not normally grow back.  Pictures of you or an exam would be needed to give you further advice as to what might improve your problem.  

If too much fat is removed, the upper eyelid can appear progressively more hollow as fat does not "grow back".  This is why we often remove very little (and often no) fat these days, especially in the central portion of the eyelid which may look hollow, over time (we've all seen celebrities with this look!)   I see many of these patients however and filler can be used (off label) to improve the hollowness of the upper lid if needed and sometimes skin tightening with devices or lasers can be helpful as well.All the best!