Let me start off by describing 100 milers with my Mother's outlook on them:
"You should really stick to the 50k's and 50 milers, I don't like the 100 milers, they just really beat you up."
My Mom's watched 5 of my 100+ mile races, and she's seen quite a lot of reasons to make the above statement. Essentially, at one point or another, I reach a point of raw, beat down, exhausted suffering. We all talk about "pushing through the pain" and experiencing deep realizations that only come about through very long runs packed with absurd amounts of adrenaline and endorphins, but there are some very dark and real moments that accompany a 100 mile race. These moments are so brutal and so painful, that even the toughest individuals are reduced to tears. Essentially a runner is stripped of all vanity, comfort, muscle fibers, etc. and they're living mile by mile at their limits; something that is rarely found in daily life, and often quickly remedied. A car accident might be over in the 20 minutes it takes the ambulance respond and to tend to your wounds. A 100 mile race's darkest moments can take several hours, and even more disturbing, no one can help you end the pain, you must continue running, often worsening and prolonging the pain until you have finished (which is the complete opposite of what seems logically right).
These moments though are not in vain though. They serve to make the finish line all the more sweeter, or to instill passion in training to avenge a DNF. The passion and emotion that one might feel at a finish line isn't a something that a blog/youtube video/Chariots of Fire montage can express. It's an extremely personal feeling of joy, pride, relief, and exaltation that no one else can ever exactly feel or express. Sure, you often get a belt buckle and a shirt, but those material items pale in comparison to brilliance of the accomplishment. It might take a few months or a few years to get over the painful memories, but inevitably the joyful memories bring most runners back to the computer to sign up for another 100 miler (which might be a reason not to sign up for your first one). As hard as it is to believe, all the suffering and painful miles are more than worth the joy of standing at the finish line.
So, why should you sign up for a 100 mile race? Well, why think of it like being a car aficionado and buying your dream luxury car. Is 100 grand a lot of pay checks and long hours at work to save up enough money to afford a Porsche? Yes, but, if it's worth it to you, and you feel really great in it, then go for it. Now in terms of running:
Do you want to run really, really, really far?
Do you want to accomplish something incredibly meaningful in endurance running?
Do you want an adventure with a capital A?
Do you want to feel intense joy from copious amounts of endorphins and adrenaline?
Do you love running in sickness and health, puking and cramping, despair and exaltation?
Well, if you do, I suggest you sign up for a 100. I promise you, you won't be disappointed. If you are concerned about an intense enough joy awaiting you at the finish line, find a race with as much climbing, technical trails, and difficult conditions as possible.
Jimmy Dean Freeman's Synchroblog
Katie DeSplinter's Synchroblog
Jen Benna's Synchroblog
Amy Sproston's Synchroblog