Timmer retired from the game at almost 38, after helping Feyenoord to the seventh place in 2008–09 campaign, having appeared in 513 matches as a professional – only in the league. However, in March 2010, as SC Heerenveen had all three first-team goalkeepers on the injured list, he went on trial with the club and signed a contract until the end of the season, contributing with nine games to an eventual 11th place-finish, and retiring for good in June.
In June 2012, Timmer was appointed as technical/commercial manager of second level club AGOVV Apeldoorn.
Timmer is married to speed skaterMarianne Timmer. After retiring in 2009, he said Heerenveen would be the only club he would play for if he decided to return, as she had previously experienced success in Heerenveen's Thialf.