Long term effects of herniated disk if untreated?

Most get better: Without any long term issues although there is a risk of another herniation over your lifetime at a 5% risk.

Longterm disc hernia: The long term effects are insignificant, unless the herniated fragment(s) are pushing on a nerve. There is no evidence that patients with herniated discs over time get more back pain. Even long standing weakness due to nerve compression can improve if the body resorbs the disc hernia, or if it get removed by surgery. Only have surgery if nerve compression is making you feel miserable!