I have been implementing the Custom Assets into my own portfolio. It went well and the feature is a great addition. My only suggestion is to add a table somewhere that lists Symbol + Most recent price date. Of course, this could also be added as a column to the existing table under the Custom Assets menu.
I am aware that the prices can also be seen through this table by clicking on Symbol + Prices. However, it would be incredibly helpful to see all Most Recent price dates at once. In this way, you can quickly identify where the Most Recent price is getting too old. If you have a bunch of Custom Assets, it will be much more efficient to bring your portfolio up to date by focussing on the most outdated price data first.