I always undo after sending segments of my edit to After Effects. This only undoes the premiere deletion and AE linking, the edit is already sent to After Effects. I have never found the linking of AE projects into Premiere to be very useful as my AE edits are usually too heavy, and I like to maintain the footage in premiere. It would be nice if Premiere had an option to send to AE without linking or deleting, but hitting undo is relatively easy.
Check out 9 Slice Scale.
A way to scale graphics while preserving the border and corners.
An FxFactory Plugin for AE, Premiere, Motion and FCP.
http://monadnock.org/9slice/