I don't believe there's any running injury that can keep you away for more than 6 weeks. I've been running for 20 years (50,000 miles) and have unfortunately been badly injured about 40 times, where I was hurt bad enough where I simply coudn't run, but things always heal in about 3 weeks avg, or if I'm lucky I can run through the pain if possible and let things heal "on the run." I've had several 6-week injuries, and they are the worst. I probably never let things heal completely because that would take way longer, but at least I get up to fast racing condition in between the injuries. The first couple weeks back from injury are the worst because of all the scar tissue I have to work through. It's amazing how I can be doing sub 5-min repeats one week, get injured then after 2 weeks off I have trouble even doing a 3-mile run in 22 min. It's so hard to come back, but I can't stand not to run. My injuries have been achilles tendonitis, plantar fascitis, strained psoas, patellar tendonitis, chronic muscle tears, anterior tibialis tendonitis, sesamoiditis, cuboid stress reaction syndrom, posterior tibial tendonitis, patellofemoral syndrome, strained spring ligament, groin strain, illiotibial band syndrome, calf tear, hamstring tear, sciatica, compartment syndrome, extensor tendonitis, etc. The list goes on and on. The only thing I've never had is a stress fracture. So, God granted me strong bones, but terrible connective tissue and muscles!
I'm amazed that I've been able to fight through the injuries so many dozens of times and am able to work my way back to fitness. I think if you love something you just endure. I'm amazed how fast people sometimes give up after 2 or 3 injuries. I only run in the 31's for 10k and I've been willing to go through the ordeal dozens of times. I often wonder what I could have accomplished if I wans't so terribly prone to injury.