I'm 53. Is is safe to have a Facelift at the same time as I replace a deflated breast implant?

The implant replacement should only take about 30 minutes, and depending on how long the facelift is it should be reasonable to combine them. You will find a wide range of times estimated for facelift surgery so it is good to know what your surgeon's total estimated surgical time is. At 53 you are at an excellent age for a natural looking facelift.

Multiple cosmetic surgical procedures involving the face and
neck are technically feasible to be performed at the same surgical event if
general anesthesia chosen. However, multiple variables like the type of
procedures (e.g. mini lift ~2 hours, vs. full malar fat pad facelift ~ 4.5
hours), total length of the combined procedures (e.g. 3 hours vs. 9 hours),
number of surgeons involved (e.g. single surgeon vs. double surgeon or surgeon
and a surgical PA), etc. should be taken into the account to determine the
safety of undergoing combined procedures during the same anesthetic event. Patients may undergo facelift under pure local
anesthesia without IV sedation or general anesthesia thus maximizing safety and
minimizing the risks associated with this last two anesthetic modalities

This is an interesting question and deserve a careful answer. When a saline implant deflates especially if there is a delay in surgery, the capsule  around the implant shrinks and a capsulotomy, often circumferential is need to avoid a harder breast after the operation. This will require a general anesthetic for most surgeon. A full facelift which typically, at least in my hands takes about three hous to do can easily be done under a local anesthetic with moderate or conscious sedation. If you were my patient I would advise you to do a short general anesthetic for the implant exchange and do the facelift at a different time. You also have to understand that the breast implant surgeon might not be the ideal choice for your facelift unless you know that he is a doctor with lots of experience in both procedures.