Is It Better To Go In For Total Knee Replacement Of Both Knees Together Or One Knee At A Time?

My mom is 59 yrs old and she has arthriritis of both knees…ie both in very bad condition…the doctor suggested getting both knees operated at the same time(4 DAYS apart)…but I read somewhere that recovery is very much delayed in such cases plus it’s difficult to do.anyone with any personal or professional experience please help!