Background: Robert Walls (born 21 July 1950) is a former Australian rules footballer who represented Carlton and Fitzroy in the Victorian Football League (VFL) during the 1960s and 1970s. In a playing career that spanned three decades Robert played a combined 259 games and kicked a total of 444 goals. Throughout the 1980s and 1990s he continued to coach in the VFL/AFL for a total of 347 games across four different clubs. As a coach, his greatest achievement came in 1987 when he coached Carlton to the 1987 VFL premiership, the same club he won premierships with as player in 1968, 1970 and 1972.
Context: Walls coached the Brisbane Bears from 1991-1995. It took until the early 2000s for Robert's style of coaching to surface as a method that had become outdated, and criticised in the football and wider community. Robert would coach Brisbane Bears for 109 games (30 wins - 78 losses - 1 draw).  It was revealed in the video "Passion To Play" that in Walls first year as Bears coach in 1991, as disciplinary action Walls authorised his players to don boxing gloves and beat 21-year-old teammate Shane Strempel repetitively in the head until he was severely bashed and bloodied after which Strempel quit playing football. Walls' coaching style was criticised about the incident by Kevin Sheedy who has several times questioned his credibility as a football coach.  In his last season, 1995, he had been told after Round 15 that with 4 wins and 11 losses for the season, he would not be re-appointed for 1996. But a major turning point in the season for the Bears soon came. In Round 16, against Hawthorn, Brisbane trailed by 45 points at 3-quarter time and ended up winning by 7, which remains a VFL/AFL record for the biggest 3-quarter time deficit turned into a win.  From there, the Bears continued their run and won 6 of their next 7 games. They found themselves in eighth position, and qualifying for the finals, after being second-last just 7 weeks earlier. They faced Carlton, the top ranked side in week one of the finals, and went down by just 13 points, a monumental achievement considering Carlton won the next two weeks by more than 10 goals to claim the premiership. Despite this turnaround, a change of heart was not considered, and Walls moved to Richmond the following year to coach.
Question: When did he reitre?

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