I point you to this brilliant piece of reporting from the Standard:
"Figures obtained by the Standard show track, signal and construction work will close or part-suspend many Tube lines every weekend until just before the Olympics.
"When a full service resumes on Saturday, 21 July 2012, there will have been a gap of four years and eight months since Tube bosses last ran a full weekend network."
Which manages to run the gauntlet between staggering and unsurprising in one.
Surely - a question echoed by Christian Wolmar in the article itself - now that TfL runs operations and infrastructure for the network it can better schedule these works?