It's all to easy to get into a routine of extended hours and weekend working through habit or some misplaced sense of 'looking busy".
Good friend of mine was posted as a SNCO to an engineering documentation establishment which was ostensibly an 8 to 5 job. On arrival he was told by his WO that hardly anyone finished at 5pm and some worked until very late to which my friend replied 'Why, aren't they very good at their jobs?' (He enjoyed the same quick wit and lack of career as I did...
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He used to finish at 5 promptly and got everything done that was asked of him. Apparently a lot of the guys he worked with just used to dawdle through the day and get everything done by 6 or half past because it looked good. The mind boggles.
I used to run the F4 CADC section at Sealand. The first thing the guy I took over from told me was to get myself a clipboard and if I had nothing to do to just wander around the section putting tickmarks on a blank piece of paper. It was good advice.