mocassins usually don't last more than a year since they're just soft flexible leather. probably the best thing for you feet though. since I've started wearing mocs my toes spread out a lot more than they used to. the first week or two sucks but they're super comfortable after that. the important parts are:
-flexible toe box that will expand to fit the width of your feet
-completely flat bottom, no raised heel. this causes you to walk naturally without heel striking, saving your knees, hips and ankles
-thin sole, if any. this helps you feel the terrain and encourages stepping lightly
if you're going to wear them in the street then get a ~4mm flat textured rubber sole. if you're only wearing them in snow or on trails then a thinner crepe can work. I've worn unsoled (one layer of leather on the bottom) mocs and they're OK except they get really slippery on wet grass and wear out really quick. Apparently there's a native moccasin guild and they get mad when people make rubber bottom mocs, but fuck em. winter mocs should have wool on the bottom or lining the whole inside.
I dunno much about the manitobah mukluks because I don't wear that kind of shoe, but the people running the company are quite nice.