Worst I've had to contend with is plantar fasciitis. Made it very difficult to play 18 holes (riding a cart no less). There were a couple of occasions when I wasn't sure I could actually walk within a few hours after finishing, as the foot pain becomes more acute after resting. Playing golf again within two days of a round was out of the question. Then I got fitted with orthotic inserts for my every day shoes, and found golf shoes (Footjoy Icons) that felt nearly identical to my regular shoes with the inserts in them. Within 2 months, It was greatly improved. The plantar fasciitis still lingers. I feel it a bit after playing 18 holes (riding), so I'm not going to be walking 18 anytime soon, but I think I could play 2 or three days in a row without issue, and I think 36 holes in a day would also be doable.