How long did the events in The Inner Light take, from Picard's point of view? It was only a few minutes for the crew members on the bridge, watching Picard, but how many years passed for Picard?
Judging by the fact that he had at least one grandchild in the scenario, I'd say something on the order of about 30 years or so, maybe a little longer.
There doesn't seem to be a definite canonical answer, I'm afraid.
Are we sure that the probe simulated 30 years of life as Kamin? Perhaps it only implanted several hundred/thousand "memories" of life as Kamin (maybe totaling several hundred hours), enough to create the illusion of a continued existence for 30 years.
This seems more technically plausible than compressing 30 years into several minutes. I'm not sure if the human brain could handle that much stimulation.