I'm one of those who is 61, dx'd at age 41, PPMS.

Maybe I'm in the minority, but my progression has been at the same rate all 20 years. Almost too predictable. I go between 2 and 3 years between the loss of functions. True examples;
1995 Dx'd after all tests: Oligloconal band -just one -.showed in LP. Bloodwork ruled out things like Lyme Disease, Deer Tick & a host of other stuff. Brain MRI showed, "lesions too numerous to count". Dizziness when standing with eyes closed, as during showers. Heat causing weakness of all extremities also bladder becoming over-active. MRI's of C and T spine. Numerous lesions, some spanning two or more vertabrae.
1998 Extreme heat weakening, using one cane to walk, left leg quits when it's tired. Still drive but must lift left leg into car.

2000 Tried using two canes because both legs too weak to operate without help. Helped for a few months. Got Rollator. Worked well for about a year, until I began falling even with it. Had to begin IC. No more bladder control.
2002 - Legs no longer "listen" to me. Had to get elevator installed in garage to get 4' up to house level. WELL worth the money.
2004 New scooter. Motor could not be fixed
2006 Second new scooter.
2008 New Pride Jazzy power chair. My left hand and arm too week to guide/drive the scooter. Gained some weight. Developed really bad edema in both feet and both ankles. Doc said I needed chair w/elevating legs and tilt to change pressure points; I had Stage 2 pressure soars on my butt. That took 6 months to heal w/help from visiting wound care nurse home visits.
2010 Oct/Nov Got suprapubic foley catheter. Got new Permobil C300 power chair. Chair rises 10", tilts and legs elevate. Definately helped with edema, but I lost weight, too.
2012 No more left hand or arm usage. Right arm weaker, won't lift above shoulder height.
2014-15 Got factory reconditioned Hill Rom Advanta hospital bed and got a good, multi-options air mattress for it. Had it a year now - still happy with it.
Bed and mattress are both awesome. No regrets.

Almost May, 2015 Legs - useless. Left arm/hand - useless. Right arm - useless. Right hand - 95% useless. No fine motor skills. Can't write. Can't hold a glass. Can't get a spoon to my mouth without spilling it's contents. Hard to stab pre-cut meat with a heavy fork; I eat with a plastic fork. Can't use any knife.

By 2016 I estimate I'll have trouble swallowing.
At that point I must consider my options. I already have my Advanced Directives. I do not want feeding or oxygen tubes, nor CPR or artificial hydration.

We'll see what's happening next year.
Karen