Soap is safe to use as long as all the lye has reacted and the soap doesn't zap. Just remember it's not at it's best and may be a little harsh feeling or drying on your skin. However, curing allows for more water evaporation, lather improves (more dense & bubbly) and for the soap to become milder. I notice a difference in 2 weeks but I still cure soap for at least 4 weeks to make sure excess water has evaporated and the soap has "hardened".
I'd say it's personal preference. If you're a bit impatient, perhaps try a bar at 2 weeks and see how it is and how it holds up in the shower. If it seems soft and is used up quickly then you know it does need a longer curing time. I don't recommend a 2 week cure normally but I can understand how hard it is to wait to test a bar. If you're going to give the soap as a gift or sell it, I strongly recommend at least a 4 week curing time. I cure soap for at least 4 weeks. I tested a regular gelled 4+ oz bar which had cured for 4 weeks and it lasted a month for me. However, I didn't use the bar every day but I used it at least 5 days every week.