There's at least one monk living this way right now!

Stylites or "pillar dwellers" have been part of the ascetic tradition of the Eastern Orthodox Church since St. Symeon the Stylite in the 5th century. His disciple St. Daniel continued the practice after St. Symeon's repose.

I'm not sure if this fits posting criteria, but without proof of Simon doing it, I can say that similar extreme acts of asceticism have been recorded throughout history. There is a "Baba" in India who has kept one arm raised for 38 years. European (Christian) asceticism usually involved extreme fasting, or hermitage (in medieval Ireland, one might find an Abbott whose church was a mud hut in the wilderness). Catholic Nuns have been known to isolate themselves in cells for extended periods of time. In Japan, certain monks would practice perhaps the ultimate form of ascetic discipline, Sokushinbutsu, where the practitioner literally mummified themselves.

So even though I can't prove Simon did stay up there for years, I would say that it is possible he did. Many many people, religious mystics or not, have undergone extreme and prolonged conditions in the name of discipline. I can't say he wide the pillar was supposed to have been, but if it was wide enough for him to lie in the fetal position, or even to sit cross-legged, I don't we why he couldn't have stayed there if he was determined enough. It is evident to me that,historically, meditation and ascetic practices have enabled people to achieve extreme feats, and Simon's sounds at least plausible.

There were (and are) indeed many pillar saints. The most famous is St Symeon the Stylite (d.459), who in turn inspired others, with St Daniel (d.493) being perhaps the most prominent of the next generation. Their Lives are full of interesting details about themselves and their contexts, and you can read them for yourself here and here. As for how they actually managed to stay on a pillar, from these contemporary accounts it sounds like each platform had a balustrade around it, so the saints can sleep and rest (albeit with some difficulty!). They are also in communication with their followers on the ground, as the two saints both built up a following before going up the pillar and their fame only increased when they decided to become stylites. Disciples and petitioners can climb up to bring up supplies and ask the saints for advice or miracles, whilst occasionally the saints themselves will also climb down if there was a particular need. St Daniel for instance famously marched into Constantinople when the usurper Basiliscus was seemingly going to adopt the Miaphysite heresy; such was the extent of Daniel's fame that he allegedly forced the emperor to stop this outrageous policy and to re-embrace orthodoxy. The truth is most likely a great deal more complicated than that, but I don't see any reason why we should dismiss this story entirely. Late antiquity was an age of holy men and asceticism, so men who did embrace the ascetic life had enormous influence, both before and after the rise of the stylites.