depends...
whether i'ts a problem also depends on your type of activity...
I'm a trainer/consultant, and my days usually are booked either 100% or 0% (with some exceptions of course)... either I'm working at a client's place or I'm giving training (= 100%), either I work from my home office (=0%)... in the first case this means that whatever urgent matter or processing will have to be done in the evening... this is not a big problem, it's just how my work is organised. I'm self employed, so processing in the evening might mean reading e-mails next to my husband on the sofa, or in front of the television!
I could have a whole week in a row going on 100%, although I try to avoid this. One thing GTD has thought me is to try keeping at least one day every week to work from my home office. If I do have a week like that, my weekly review the week before will help me make sure I am as ready as I can be...
Myriam