Hi, Chanc93:
Radiation does not "wear off." However, any treatment -- radiation or microsurgery -- has the potential to leave one or more cells of the tumor alive, and that can result in regrowth (typically years after the treatment was performed). Studies have shown that the rate of tumor recurrence between microsurgery and radiation are virtually the same (roughly 2%) when performed by the most experienced surgeons. If you troll this forum's archives, you'll find several examples of both radiation and surgery recipients who have had their tumor resume growth years after treatment, requiring a new round of radiation or surgery.
There is only one confirmed example I've seen in medical literature of a person developing a cancerous tumor in the same location as they were irradiated years prior. On that basis, your risk of developing cancer from radiation treatments is virtually nil. However, radiotherapy is new enough (nevertheless used for many decades) that I don't believe there are studies covering a 70-year span of research; as you would be 93 years old 70 years from now, it's theoretically possible that you could develop a cancer decades from now that research could not have predicted due to its relatively short followup history. One other thing to consider is that radiation doses are much lower now than they were during the early years of its use, and fractionating (splitting a single dose up into smaller, more easily tolerated doses) also theoretically makes radiation somewhat safer. Both of those factors theoretically reduce your risk of cancer developing due to receiving radiotherapy.
From your post, it sounds like you're aware that decompression (partial removal of the tumor) won't stop the tumor from growing, and further treatment would be required to accomplish that. I suggest you ask Dr. Friedman what additional treatment he would advise.
Personally, I would not wait until you develop facial paralysis to get treatment (this is just my inexpert opinion). That's what treatment is meant to prevent, and there's no guarantee that treatment will reverse those symptoms. Even should you choose to have microsurgery to (hopefully) totally remove the tumor, and even if that surgery doesn't nick your facial nerve, the facial nerve's function can be negatively impacted from the trauma of surgery (scraping the tumor off the nerve).
It's a lot to think about. We all commiserate with your predicament, having had to make the difficult choice ourselves as to what kind of treatment we will have and when. Ask more questions of your doctors to get as clear as you can about your options and their predicted chance of success before you decide. Good luck!
Best wishes,
TW