It depends on how much you do. If you need to book travel once a year, then it is clearly easy to do it yourself. I used to work in a place that had a secretary available for these tasks. I would just give her a pile of receipts and get a check a few days later. The secretary would make reservations and schedule important meetings. This can save a huge amount of time over the years. Nowadays all these little tasks combined consume a lot of time we should spend doing real work.