Good for you, I agree that it's a nice little thing to have, though at my last employer the expenses would sometimes get held up, which was not cool. Now I expense about $400 a month, and only submit expenses quarterly because I'm lazy.
But one thing that has worked really well for me is using the DO Camera app on my iphone, with a recipe that saves the picture to an expenses folder in my Dropbox, with the file name as the date/time of the photo. So this way, immediately I incur an expense, I open the app and take a photo of the receipt. Then when I go to file the expenses in Excel, I paste in my Amex statement list and match the photo to the expense date, easy peasy.
Much less common now for me to forget about any expenses I incur. The biggest problem is when the place doesn't take Amex, and I use my personal Visa instead (I reserve my Amex for company expenses, but it is a personal card). But the DO Camera app has helped in this regard, too. But I do end up poring over my visa statement to make sure I don't forget anything.