I never did actually use 'excess salt' method... I don't think I've ever used more than 2% salt in any of my cures. I also tend to keep Nitrite levels at or very close to the USDA rules, so I really never went beyond 200 PPM and pretty regularly stay at 120 PPM. So, I'm effectively doing a equilibrium style of cure...
What I've observed is that for something really lean like pork loin, for 'Canadian bacon' , the cure will get to the center easily in 5 days... I feel I could go as many as 14 days without any problems. My ideal time would be 7 days on most pork loin.
With Pork belly, it can be a little different , because of fat layers... fat acts like a pretty darn good barrier to the cure getting deep into the meat, so the more fat , the longer it takes. Most of the pork belly I get is pretty lean and around 1.75" thick and for this , I pretty much go with the same time frame as pork loin... from 5 to 14 days with 7 days being pretty sure bet that the cure penetrated all the way to the center. For a thicker belly and/or one that has a lot more fat, I'd probably be willing to add 2 to 3 days longer, where 10 days would likely be what I would shoot for on a thicker/fattier belly... but still I would not likely ever go much beyond 14 days, not because I was worried about over curing, but because I just don't think it's a good idea... Having said that , if for some reason on the 14th day I just couldn't get around to smoking the cured belly , I'd have no real problem extending out to 18 days or so and wouldn't really worry about it being unhealthy or even 'bad'.
If your using too much salt, or worse yet, way too much Nitrite or nitrate all bets are off... If I accidentally put in like 500 PPM nitrite or more... I'd probably just scrap the batch... with too much salt, i'd probably try to soak it in fresh water to save it.