Bradley Wood will serve a six-year suspension from football and all football activity from 9 March 2018 to 8 March 2024 after committing 25 breaches of The FA’s Integrity and Betting Rules. http://www.thefa.com/news/2018/apr/19/bradley-wood-lincoln-suspended-190418 I had a quick search and the only ban that I can that was longer, was Man United player Enoch West, who was banned for life in 1915 (also for betting irregularities), with the ban being lifted in 1945, by which time he was 59.
High profile (then) Peter Swan, Tony Kay and David Layne (Lane?) of Sheff Weds in the 60's betting scandal. All 3 actually did time and Swan missed out, so they say, on a possible World Cup place in 66.
And whilst we're on about betting misdemeanours, I see Joseph Anthony Barton was unveiled as the new Fleetwood boss yesterday .... to start one day after his ban ends in June