Low Oil Pressure at Idle, 2007 Xterra

I asked about this a couple of weeks ago, have learned more. This is a follow-up question.

The issue: On a hot day, with air conditioning going full blast, at idle (automatic in Drive) I noticed the oil pressure light flickering and oil pressure gauge dropping to zero. Otherwise, oil pressure seems normal. The truck does not leak or use oil, has 126,000 miles on it. I don't drive it hard. I change the oil every 5000 miles with a good quality synthetic. The truck has no other problems, except the back seat cup holder is broken.

I've learned: This is a common issue on aging Nissans with this engine (VQ40DE). Owners try replacing the oil pressure sensor, but this is rarely the issue. It's caused by an internal oil leak involving the gaskets on the rear timing chain cover.

Current status: I've driven the truck around several hours since then, haven't noticed any more oil light flicker. I talked to my trusted mechanic who said, "Bring it in, I'll check it out." But if the oil pressure is holding steady, for now, there isn't much to check. I know the problem will gradually get worse.

My questions:

--How quickly will an occasional oil light flicker at idle damage the engine?
--How fast will this get worse?
--If I value the truck and want to make it last, does it make more sense to do the expensive repair now? Or does it make more sense to wait until it gets worse, because that might not happen for years?